EPIROBIA. 59 



mm. long, 11 wide. There is some variation in the length of 

 the free portion of the last whorl and in the proportion of 

 breadth to length, sufficiently shown in the figures. 



Genus EPIROBIA Strebel & Pfeffer, 1880. 



Epirobia STREBEL, Beitrag zur Kenntniss der Fauna Mexi- 

 kanischer Land- und Siisswasser-Conchylien, iv, pp. 77, 85, 

 E. berendti, polygyra, morini-polygyrella, apiostoma. PILS- 

 BRY & VANATTA, Proc. A. N. S. Phila., 1898, p. 281, type E. 

 polygyra. Cylindrella and Holospira of some authors. 



Shell thin, brown or corneous, rimate, many-whorled, re- 

 taining the apex complete ; slender and lengthened, attenuated 

 above, with the last whorl straightened and shortly free, not 

 carinate at the base. Apex obtuse, several succeeding whorls 

 not increasing in diameter, smooth; following whorls striate 

 or costulate (pi. 18, fig. 37). Internal axis rather slender but 

 hollow, sculptured with longitudinal white streaks or irregular 

 lamellae, or granules formed by their dislocation and inter- 

 ruption. 



The genital system (pi. 19, fig. 48, E. apiostoma) is imper- 

 fectly known from data obtained by Strebel & Pfeffer from 

 a dried specimen. A branch of the main right retractor band is 

 inserted on the atrium, and a long, band-like gland is accessory 

 to the vagina. This gland is apparently lined with gigantic 

 mucous cells (pi. 19, fig. 49), and its cavity communicates with 

 that of the vagina. Only the lower portion of the sperma- 

 thecal duct is shown. The penis has a stout retractor muscle 

 laterally inserted, the vas deferens being apical. 



The jaw is unknown. The radula of E. polygyra (pi. 50, f. 

 6, 7) is strap-shaped, bearing 18.1.18 teeth in slightly curved 

 and sinuous transverse rows, which near the edges become 

 more oblique. The middle row consists of teeth with the basal 

 plate short and square, the very broad, rounded middle cusp 

 projecting beyond it, side cusps small, basal, and separated 

 from the mesocone. The adjacent lateral teeth are similar 

 except that the entocone is wanting. The passage from lat- 

 eral to marginal teeth takes place by the large cusp becoming 

 more acute, then developing an inner spur or entocone, which 



