1920.] NATURAL SCIENCES OF PHILADELPHIA. 7 



ANCYLID^. 

 Uncancylus calverti n. sp. Fig. 4. 



Brook near Rio Reventazon, Juan Vinas, 2500 ft., Apr. 28, 1910. 

 Type and paratypes, No. 105277, A. N. S. P. 



The shell is oval, moderately elevated, the altitude half the width, 

 the apex acute, recurved or hooked, at the posterior fourth of the 

 length and about half way between the median line and the right 

 margin. The anterior and left slopes are convex above, nearly 

 straight near the margins; posterior strongly concave, the right 

 slope much less so. Isabella colored, rather opaque, not glossy. 

 Sculpture of many raised striae radiating from the summit, a few 

 in the middle, anteriorly, coarse, the rest fine and narrow; on the 

 sides and behind they are scarcely to be seen except by transmitted 

 light. The interior has a translucent-whitish layer. 



Length 7.4, width 4.6, alt. 2.3 mm. 



Ancyckis conccntricus Orb., which appears to be nearly related, 

 is less symmetrical in contour, with the apex further towards the 

 right, and with about the same length it is more elevated. 



Ancyclus radiatus Guilding,^ which is known to me only from 

 Guilding's account, resembles A. calverti in sculpture, but it is 

 narrower relative to the length, if Guilding's figures are accurate; 

 moreover, the apical part is not abruptly narrowed near the tip, 

 as it is in XJ . calverti. Practically all authors who have considered 

 the question agree in considering A. excentricus Morel, identical 

 with A. radiatus. The former is a well known species, quite dis- 

 tinct from U. calverti. 



The writer is indebted to Dr. Bryant Walker for reviewing the 

 determination of this species, and indicating differences from A. 

 radiatus. He also called attention to an error in H. & A. Adams, 

 "Genera of Recent Mollusca", II, p. 265, pi. 84, fig. 5, said to rep- 

 resent A. radiatus, but really copied from one of Guilding's figures 

 of A. irroratus. This mistake has been perpetuated in the works 

 of Bourguignat and Clessin. 



The genus Uncancylus is new to North America. The known 

 species are chiefly Brazilian. It was proposed for South American 

 Ancyli with the spire strongly hooked towards the right side, the 

 shell therefore sinistral. Type Ancylus harilensis Moric' 



8 The Zoological Journal, III, 1828, p. .536, Suppl. pi. 26, figs. 7, 8, 9. On 

 dead leaves in ditches, St. Vincent. 

 » Proc. A. N. S. Phila., 1913, p. 671. 



