Species keys (arranged alphabetically by genus)

1a. Protoconch surface smooth; ribs weak, irregular; spiral color bands present 1b. Protoconch with distinct cross-hatching; ribs strong, regular; color bands (if present) transverse 2a. Shell height >½ shell diameter; 3+ ribs per mm on body whorl 2b. Shell height <½ shell diameter; 2½ or fewer ribs per mm on body whorl

1a. Shell width 2/5 of height 1b. Shell width 1/3 of height 2a. Shell surface completely smooth 2b. Shell surface distinctly striate 3a. Shell height >1.5 mm; body whorl distinctly wider than penultimate 3b. Shell height <1.5 mm; body and penultimate whorls of approximately same diameter 4a. Striae strong with sharp edges, peristome unthickened 4b. Striae weaker with rounded edges, peristome moderately thickened

1a. Shell >1.9 times as tall as broad, color light red-tan, resticted to fens 1b. Shell <1.8 times as tall as broad, color grey-green to tan, habitats various 2a. Shell averaging >7mm tall, growth lines indistinct; tan-brown color; moist, open habitats 2b. Shells averaging <7mm tall, growth lines relatively distinct, gray-green color

1a. Mature shells >2.3 mm wide, broadly ovate shape 1b. Mature shells < 2.3 mm wide, elliptical shape 2a. Mature shells <6 mm tall; deep suture with rounded whorls; shell translucent brown 2b. Mature shells >6 mm tall; shallow suture with flattened whorls; shell transparent, yellow

1a. Shell cylindrical; apex domed; adult shell with 6-7 whorls, >2½mm tall 1b. Shell tapered; apex conical; adult shell with 5½-6½ whorls, <=2½mm tall

1a. Lamella present on columellar side of aperture 1b. Lamella absent 2a. Ribs indistinct or lacking on shell base 2b. Ribs distinct on shell base 3a. Umbilicus >1/3 shell diameter 3b. Umbilicus 1/3 shell diameter or less (Pleistocene fossil only in the upper Midwest) 4a. Angular body whorl margin 4b. Rounded body whorl margin

1a. Whorls gradually increasing in size, with last 3 constituting <2/3 of total shell diameter as seen from top; spiral lines cutting through stirae on protochonch 1b. Whorls increasing rapidly in size, with last 3 constituting >2/3 of total shell diameter as seen from top; distinct ribs and spiral lines present on initial whorls 2a. Protochonch luster shiny with reduced striation; dark brown-copper colored; spiral lines on base as or more distinct than transverse lines 2b. Protochonch luster silky with crisp striation; tan to light-brown color; spiral lines on base less distinct than transverse lines

1a. Shell <3¼mm tall; ovoid-conical; color white to brown 1b. Shell >3¼mm tall, cylindrical or barrel-shaped; translucent white when fresh (subgenus Albinula) 2a. Angulo-parietal lamella a simple peg-like tooth 2b. Angulo-parietal lamellae not peg-shaped 3a. Angulo-parietal lamella a single large, folded sheet 3b. Angular and parietal lobes of angulo-parietal lamellae distinct 4a. Fresh shells whitish 4b. Fresh shells brown-red 5a. Columellar lamella triangular or round in cross section 5b. Columellar lamella a more or less vertical, folded plate 6a. Columellar lamella with both forward and basally pointing components, appearing more or less pyramidal in apertural view; shell usually >4 mm tall 6b. Columellar lamella lacking a basal lobe, making the entire structure appear as a downward-pointing peg in apertural view; shell <4 mm tall 7a. Shell narrowly conical, with height more than 1� times width; lower palatal lamella deeply entering aperture 7b. Shell broadly conical, with height less than 1� times width; lower palatal lamella not deeply entering aperture 8a. Basal and palatal lamellae absent; shell >2.4 mm tall 8b. Basal and palatal lamellae present; shell <2.0 mm tall 9a. Angular lobe separate and parallel to parietal lobe throughout 9b. Angular lobe pointed towards and fused to the middle of the parietal lobe

1a. Shell openly umbilicate 1b. Shell very narrowly rimate 2a. Shell with evenly-spaced impressed ribs, color clear-white, spiral striation absent 2b. Shell with irregular impressed ribs, color honey-yellow, spiral striations present

1a. Callus thickening present inside of shell 1b. No shell thickenings present inside of shell

1a. Surface shiny and smooth or with microscopic spiral lines 1b. Surface dull with large, raised spiral lyrae 2a. Umbilicus deep (usually extending beyond ½ of shell height) and wide (½-1/3 of shell diameter) as seen in mature individuals; somewhat domed spire 2b. Umbilicus shallow (rarely extending beyond ½ of shell height) and narrow (1/3-¼ of shell diameter) as seen in mature individuals; flat spire 3a. Callus present inside shell without lamellae 3b. Lamellae present inside shell without callus 4a. Body whorl width (on bottom) <1 mm wide; umbilicus very wide (>2/3 shell diameter) and shallow (<½ shell height) 4b. Body whorl width (on bottom) >=1 mm; umbilicus less wide (<2/3 shell diameter) and deeper (approximately ½ shell height)

1a. Shell diameter >18 mm 1b. Shell diameter <=18 mm

1a. Umbilicus <1/10 shell width 1b. Umbilicus >=1/10 shell width 2a. Whorl and protoconch surface nearly smooth; glassy luster 2b. Whorl and protoconch striate; dull luster 3a. Body whorl absent or with only indistinct spiral lines 3b. Body whorl with distinct spiral lines 4a. Umbilicus open, 1/5-1/6 shell diameter 4b. Umbillicus rimate, 1/7-1/10 shell diameter

1a. Shell with distinct spiral color bands 1b. Shell of uniform color 2a. Diameter >20mm 2b. Diameter <20mm 3a. Parietal lamellae >1/3 aperture length, shell almost as tall as wide 3b. Parietal lamellae <1/3 aperture length or absent, shell clearly wider than tall 4a. Parietal lamella present; final 3 whorls constituting <80% of shell diameter 4b. Parietal lamella absent; final 3 whorls constituting 80% or more of shell diameter 5a. Pronounced thickening on peristome base near columella 5b. Peristome thickness essentially constant throughout

1a. Shell brown, >4½mm diameter at 4½ whorls 1b. Shell whitish, <4mm diameter at 4½ whorls

1a. Width of final segment of body whorl 2x that of adjacent section of penultimate whorl; shell diameter generally >11mm; shell luster not too glossy 1b. Width of final segment of body whorl ~1.5x of adjacent section of penultimate whorl; shell diameter generally <11mm; glassy shell luster

1a. Penultimate whorl (as seen from bottom) low convex, with maximum width <=½ the maximum aperture width; aperture approaching maximum width in upper ½ of shell 1b. Penultimate whorl (as seen from bottom) more highly convex, with maximum width 2/3-¾ of the maximum aperture width; aperture approaching maximum width at ½ of shell height 2a. Shell width >½ of shell height; shell apex angle >75° (e.g. 3 shells lined up like pie wedges with apices touching makes more than ½ of a circle) 2b. Shell width <=½ of shell height; shell apex angle approximately 60° (e.g. 3 shells lined up like pie wedges with apices touching makes ½ of a circle or less)

1a. Lamellae consisting of separate pegs 1b. Individual lamellae fused into a single callus ridge

1a. Umbilicus <¼ shell diameter, rimate; hairs on shell surface 1b. Umbilicus >1/3 shell diameter, shells without hairs 2a. Margin of shell angular 2b. Margin of shell rounded 3a. Upper palatial lamella deeply immersed; parietal lamella with straight-sided, angular channel down middle and a tri-lobed terminus 3b. Upper palatial lamella only moderately immersed; parietal lamella with rounded, concave channel down middle and with square terminus

1a. Shell approximately twice as tall as wide 1b. Shell approximately 1.3 times as tall as wide

1a. Lamellae present on base of aperture 1b. Lamellae absent 2a. Umbilicus >1/3 shell diameter 2b. Umbilicus <=1/3 shell diameter 3a. Shell >1.2 mm diameter and >¾ mm tall; color deep rust-brown 3b. Shell <=1 mm diameter and <=½ mm tall; color tan to gray 4a. All ribs of essentially equal size, spearated by 1-3 minor riblets 4b. Some ribs more prominent than others, separated by 5+ minor riblets

1a. Lower margin of peristome complete (Euchemotrema) 1b. Lower margin of peristome with notch removed (Stenotrema) 2a. Shell margin angular 2b. Shell margin rounded 3a. Body and penultimate whorls >1¼ mm wide as measured from top of shell 3b. Body and penultimate whorls <=1¾ mm wide as measured from top of shell 4a. Shell umbilicate; <8½ mm diameter 4b. Shell imperforate; >=9 mm diameter 5a. Right end of parietal lamella entering aperture; aperture less wide than basal peristome lip 5b. Right end of parietal lamella barely entering aperture, aperture as wide as basal peristome lip 6a. Aperture wider than basal peristome margin; shell >= 8 mm diameter; interior lamella at the junction of the columella and aperture extending >1 mm beyond basal peristome margin; approximately 4 shell hairs per mm 6b. Aperture same width as basal peristome margin; shell approximately 6 mm diameter; interior lamella at the junction of the columella and aperture extending <1 mm beyond basal peristome margin; 5-6 shell hairs per mm

1a. Shell diameter <2mm 1b. Shell diameter >2mm 2a. Sprial lines prominent on protoconch 2b. No sprial lines on protoconch 3a. Prominent, widely spaced ribs, umbilicus 1/3 diameter, whorls increasing slowly 3b. Ribs and spiral lines weak, umbilicus 1/5 shell diameter or less; whorls increasing rapidly

1a. Margin angular, shell pyramidal, 3-4 basal folds 1b. Margin rounded, shell beehive-shaped, 5+ basal folds 2a. Basal folds of equal size, arranged in smooth arc 2b. Basal fold size unequal with second from umbilius much longer than first, folds arranged in an irregular arc

1a. Shell apex angle >60° 1b. Shell apex angle <60° 2a. Mature shell length >15 mm; shell thin and usually translucent 2b. Mature shell length <15 mm 3a. Shell surface irregular; shell thick and almost opaque 3b. Shell surface smooth; shell thin and transparent 4a. Mature shell length >15 mm 4b. Mature shell length <15 mm

1a. Parietal lamella pointed below palatial 1b. Parietal lamella pointed at or above palatial 2a. Shell surface smooth and shining; flat spire 2b. Shell surface striate and dull; domed spire

1a. Peristome unthickened in mature shells 1b. Peristome strongly white-thickened in mature shells 2a. Shell surface smooth, shiny, major ribs absent 2b. Shell surface dull, major ribs present 3a. Shell white; ribs low but distinct; diameter of minor axis in mature shells >1½ mm; body whorl diameter remaining relatively constant at aperture so that last portion of whorl remains approximately parallel to penultimate 3b. Shell yellow-tan; ribs indistinct or lacking, making shell appear smooth; diameter of minor axis in mature shells <=1½ mm; body whorl diameter increasing rapidly at aperture so that last portion of whorl diverges from penultimate 4a. Diameter of mature shells <=2mm 4b. Diameter of mature shells >2mm 5a. Diameter of mature shells <2½mm, 23-35 ribs on body whorl, ribs > 0.1 mm tall 5b. Diameter >2½mm, 45-50 ribs on body whorl, ribs <0.1 mm tall

1a. Umbilicus rimate, less than 1/10 shell diameter; shell diameter >6 mm 1b. Umbilicus open, more than 1/10 shell diameter; shell diameter <6 mm 2a. Basal lamellae present 2b. Basal lamellae absent 3a. Strong spiral striate on last whorl; shell surface dull below 3b. Spiral striae on last whorl indistinct, limited to base of whorl; shell surface glossy below 4a. Palatial lamellae present 4b. Palatial lamellae absent

1a. Shell surface smooth or weakly striate 1b. Shell surface strongly striate 2a. Six or more apertural lamellae 2b. Five or fewer apertural lamellae 3a. Basal lamella absent 3b. Basal lamella present 4a. Parietal lamella pointed directly at lower palatal lamella, so that parietal, lower palatal, and columellar lamellae form a cross; shell conical 4b. Parietal lamella pointed at upper palatal or space between the upper and lower palatals; shell ovoid or columnar 5a. Lower palatal lamella inserted near aperture margin so that only short axis is visible when seen in apertural view 5b. Lower palatal lamella inserted more deeply into shell so that long axis is visible when seen in apertural view 6a. Angular lamella absent; palatal wall with callus and light-colored crest; shell dull 6b. Angular lamella present; crest not light-colored; shell shiny 7a. Adult shell with ~6 whorls; aperture less than 1/3 of shell height 7b. Adult shell with ~4 whorls; aperture 1/3 or more of shell height 8a. Shell >2.0 mm tall; lower palatal lamella a straight blade 8b. Shell <1.8 mm tall; lower palatal lamella curved and deeply entering aperture 9a. Three or four apertural lamellae 9b. Five apertural lamellae 10a. Shell height >2¼ mm 10b. Shell height <2¼ mm 11a. Body whorl inflated, making shell height less than twice the width; shell color with slight greenish cast; distinct spiral striation on body whorl; aperture margin usually dark olive-brown to black 11b. Body whorl not greatly inflated, making shell height approximately twice the width; shell color honey-yellow; no spiral striation on body whorl; aperture margin not darkened 12a. Shell >2¼ mm tall; angular lamella present 12b. Shell <2¼ mm tall; angular lamella absent 13a. Shell height less than twice the width, basal lamella present 13b. Shell height twice the width or more, basal lamella absent 14a. Shell weakly striate; single depression behind aperture over both palatal lamellae 14b. Shell smooth; separate slight depressions under each palatal lamellae, or none 15a. Shell surface dull; strong crest; light-colored callus on palatal wall 15b. Shell surface shiny; crest less prominent; callus of same color as shell 16a. Shell >2¼ mm tall, shiny with weak striae 16b. Shell <=2¼ mm tall, shell dull with distinct striae 17a. Shell shape conical with body whorl much wider than the penultimate; color deep cinnamon-red; crest absent; shell striation irregular in strength and spacing 17b. Shell shape ovate with body whorl approximately the same width as the penultimate; color yellow-red brown; crest present; shell striation uniform 18a. Striae indistinct, with shell often appearing smooth under low (x10) magnification; single deep depression over both palatal lamellae; ~1¾ mm tall 18b. Striae distinct, with shell not appearing smooth under low (x10) magnification; palatal depression weak or absent; most forms >1¾ mm tall, with small southern Appalachian forms being ~1¾ mm tall 19a. Callus surrounding at least the upper palatal and often the entire palatal wall; ranging from eastern Ontario to Alaska and south to New Mexico 19b. Callus absent on palatal wall 20a. Columellar lamella more massive than the parietal; angular lamella strong; lower palatal lamella so deeply inserted that most of it is obscured by the columellar wall; striation fine and sharp 20b. Parietal lamella more massive than the columellar; angular lamella weak or absent; lower palatal lamella less deeply inserted so that most is observable in apertural view; striae somewhat rounded 21a. Basal and weak angular lamellae often present; ranging from the Upper Mississippi River valley to eastern Ontario 21b. Basal and angular lamellae often absent; ranging from Newfoundland and central Manitoba to northern Minnesota, northern Wisconsin and the New England states; also in Alaska and the Yukon

1a. Umbilicus covering over ¼ of shell diameter; upper surface dull, ribbed 1b. Umbilicus covering less than 1/5 of shell diameter, upper surface shiny, ribless 2a. Shell luster satiny from microscopic spiral lines; aperture elliptical; shell yellowish 2b. Shell luster glassy, microscopic spiral lines absent; aperture round; shell rusty-brown