454 



DESCRIPTIOlSrS OF NEW SPECIES OF FOSSILS FROM THE 

 PLATYCEEAS BREVE Simpson, n. sp., Fig. 23. 



Shell of medium size, apex not incurved ; body straight ; rapidly increasing in 

 size ; -width at the base equal to the length of the anterior side ; length of the poste- 



A.P.S. 



Tr.l889. 



rior side from two-thirds to four-fifths that of the anterior ; both sides convex ; on 

 the anterior side there is a prominent subangular elevation, commencing at the apex 

 and continuing to the base ; on each side of the carina a slight depression ; other 

 portions of the shell without plications or elevations. 



Aperture circular; peristome, as far as can be ascertained, not sinuous. 



Surface marked by elongate pustules, subregularly arranged, giving to the sur- 

 face the appearance of being coarsely striated, three in the space of 5 mm. Thei'c 

 are also faint indications of concentric striae. 



A specimen of average size measures as follows : Diameter of aperture 23 mm.; 

 length of the anterior side 20 mm.; of posterior 15 mm.; height 15 mm. 



The characteristics of this species are the short conical form, the rapid enlai-ge- 

 ment from the apex to the base, and the elongate pustules of the surface. 



From those species having a carina it is distinguished as follows: From Platij- 

 ceras carinatum by its conical form, the straight apex, the absence of plications and 

 the non-sinuosity of the peristome ; from Platyceras mitelliforme by its larger size, 

 conical form and the ornamentation of the surfjice ; from Platt/ceras conicum by its 

 shorter form and the absence of conspicuous plications and the consequent non-sinu- 

 osity of the peristome. It most closely resembles Platyceras dorsale of this forma- 

 tion, but it is shorter, much less oblique ; posterior side straight or convex ; the apex 

 more central and does not project beyond the base, while in that species the apex 

 projects beyond the base a distance nearly equal to half the diameter of the aperture. 



Formation and locality. Chemung group, near Warren, Warren county, Penn- 

 sylvania. 



^ PLATYCERAS DORSALE Simpson, n. sp., ig. 24. 



Shell obliquely subconical ; anterior side curved ; posterior straight or concave ; 

 apex not incurved, laterally compressed ; body of the shell regularly increasing in 



