Figures 6N, O; 8H; 9B,E; 14H, I; 15J, K; 16G, H; 17L–O; 18C, D.

Type material

Holotype: AMS C.439396, Bauhaus, Persephone streamway, stn 8, 23 DEC 1991.

Paratypes: AMS C.201463, same data, 30+ (11 dry, 20+ wet); QVM, 9:20540 (5 wet); AMS C.439397, same data (Fig. 14H).

Other material examined (all AMS)

Bauhaus: C.438369, stn PB6­1 (5 dry); C.201821, main streamway, stn PB6­1A (10 dry, 20+ wet); C.166856, Persephone Pot, stn PB17­8R (5 dry, 25 wet); C.201812, same locality, middle and upper streamway, stn PB17­2a.2 (20+ dry, 20+ wet); C.438370, C.201816, same data (20+ dry, 20+ wet); same locality, PB17­2A (20+ dry); C.201454, Persephone, stn 7 (4 dry, 20+ wet); C.201468, Persephone streamway, stn 9 (15 dry, 20+ wet); C.201484, same locality, stn 10 (6 dry, 20+ wet).

Damper Cave: C.203682, Main streamway near entrance, stn PB1­1A (3 dry, 5 wet); C.201458, main streamway, stn 6 (14 dry, 20+ wet).

Etymology

Progenitor Latin, founder of a family, ancestor. Refers to the apparently basal position (and plesiomorphic nature) of this species in relation to the other taxa included in Pseudotricula.

Description

Shell (Fig. 6N, O; 14H, I; 15J, K). Length up to 2.8 mm; elongate­conic (SW/SL 0.50– 0.64, mean 0.56, n = 22); spire tall, straight to slightly convex in outline; subsutural indentation on last two whorls; periphery of last whorl evenly rounded; suture simple. Protoconch (Fig. 6N) as for genus, microsculpture largely obscured in available material. Teleoconch up to 4.0 whorls in adult; umbilicus absent in juveniles; aperture oval to pearshaped; small, shorter than spire (AL/SL 0.34–0.49, mean 0.40, n = 22); outer lip orthocline to opisthocline, weakly thickened in adult, straight, usually with slight reflection; posterior notch absent; inner lip thin to moderately thickened and of narrow to medium width, in partial contact or narrowly separated from parietal wall.

Dimensions. See Table 9.

Operculum (Fig. 16G,H). Inner surface with or without white smear.

Eyes. Unpigmented.

Pallial cavity (Fig. 8H). Ctenidium narrow; 9–10 very small filaments; osphradium between posterior end and middle of ctenidium; hypobranchial gland thick to moderately developed; renal organ extends forward ca. ½ into pallial cavity; pericardium more than ½ in pallial roof.

Radula (Fig. 17L–O). Central teeth: dorsal edge with moderate to deep indentation; 5–6 lateral cusps, median cusp narrow, sharply pointed, about twice as long as adjacent cusps. Lateral teeth: dorsal edge with shallow indentation; with 5–6 cusps on outer and 4– 5 on inner side; median cusp narrow, sharply pointed, less than twice as long as adjacent cusps; ratio of cutting edge to shaft about ¼; basal projection bluntly pointed. Marginal teeth: Inner with 25–29 cusps; outer with 22–28 cusps.

Stomach (Fig. 9E). Stomach with posterior chamber and anterior chamber about equal in size or posterior chamber a little smaller.

Male genital system. Testis of 0.9–1.5 whorls; prostate gland oval to kidney­shaped; compressed in section. Pallial vas deferens straight. Penis (Fig. 9B) with weak swelling in mid­distal portion; distal end long, papilla­like; medial section tapering to parallel sided; of medium length; penial duct in medial section of penis strongly undulating; base of penis moderately wide; with moderate folds; penial duct strongly undulating.

Female genital system (Fig. 18C, D). Ovary of 0.5–0.7 whorls; oviduct extends to posterior edge of bursa copulatrix; joins bursal duct in front of posterior pallial wall at junction of albumen and capsule glands to half way between posterior pallial wall and capsule gland. Bursa copulatrix large, extending to posterior pallial wall; globular to pyriform; with bursal duct arising from middle of anterior edge of bursa, straight or with undulations. Seminal receptacle at middle of inner wall of bursa copulatrix; pyriform. More than half of albumen gland in front of posterior pallial wall; capsule gland about same length as albumen gland; compressed oval in section; anterior end blunt; ventral channel with distinct muscular vestibule; genital opening overlapping anterior end of capsule gland.

Distribution and habitat Bauhaus and Damper Cave in low energy small streams with mixed substrate. Remarks

Pseudotricula progenitor shares characters of both Nanocochlea and Pseudotricula. The small­sized, tall­spired shell is typical of Nanocochlea but the (narrowly) reflected outer lip, straight spire outline and subsutural indentation are characters found in typical Pseudotricula taxa. The protoconch microsculpture, while not able to be examined in detail, appears to be of the plesiomorphic type (shared by Nanocochlea and Pseudotricula s.s.), as are the radular characters, which are like those of Nanocochlea and P. arthurclarkei and P. conica. It is probable that this species most closely resembles the ancestral Pseudotricula that gave rise to the Precipitous Bluff cave radiation.