1905.] NATURAL SCIENCES OF PHILADELPHIA. 573 



mesocone and small ectocone as usual. The marginal teeth are short 

 and broad, with the mesocone oblique, and the ectocone split into two, 

 three or four minute, acute denticles. 



The known species are from Oahu. 



P. Wesley i Sykes. P. petasus Anc. 



P. digonophora Anc. 



Two other species were referred to this group by the senior author in 

 1893: Flelix prostrata Pse. and //. dcpressiformis Pse.,^ both described 

 from the ''Central Pacific Islands," and neither figured nor seen by 

 any subsequent author. Mr. Sykes did not find them in the British 

 Museum collection ; they arc not in the collections at Philadelphia or 

 Washington, nor is any trace of them to be found in the Pease collection 

 at Cambridge, Massachusetts.^ We learn from labels in the Academy 

 collection that Andrew Garrett knew them not. While there cannot 

 be much doubt that prostrata and depressiformis were based upon 

 species of Ptcrodiscus much like wesleyi and digonophora, it must be 

 admitted that the diagnoses are insufficient for positive identification; 

 and in the absence of types, the names must be regarded as defunct. 

 The three species known are quite distinct, being characterized as 

 follows : 



1. — Spire low-conic, with projecting, mucro-like apex; aperture small, 

 as high as wide, the peristome expanded, nearly continuous; 



umbilicus ample, P. petasus. 



2. — Spire flat or nearly so, the apex not raised. 



a. — XJmliilicus very large, broadly conic, the base strongly angular 



around it, P. digonophorus. 



h. — Umbilicus comparatively narrow, tubular, ... P. wesleyi. 



Pterodiscus wesleyi Sykes. PL XXXIX, figs. 7. 8, 9. 



Emlodonln (Ptcrodiscus) alnta Pl'r., Pilslny, Manual of Conch., IX, p. .36, 

 PI. 4, fig. 44 (no specific description or measurements). 



Endodnnta (Ptcrodiscus) wesleyi Sykes, Proc. Mai. Soc. Lond., II, p. 127, 

 1S96, based upon preceding reference. Pterodiscus wesleyi Sykes, Fauna 

 Hawaiiensis, Molk, p. 292. 



Shell umbilicate, thin, flat above, convex beneath, carinated periph- 

 erally, brown with some irregular yellowish streaks, nearly lusterless. 

 Whorls 3^, the first perceptibly convex, the rest somewhat flattened, 

 sculptured with fine oblique growth-lines only. Last whorl carinated, 

 the keel bearing an irregular flange or 'Sving" of adhering earth; base 



* Described in Proc. Zool. Soc. Land., 1860, p. 670. On p. 675 H. depressiformis 

 is said to be H. alata Pfr., on Cuming's authority. 



' We are indebted to Dr. William H. Dall, of the National Museum, and Dr. 

 W. Faxon, of the Museum of Comparative Zoology at Cambridge, for examining 

 the collections under their charge for these species. 



