665 Platyc. 



Platyceras breve, neiv species^ Simpson, Trans. Amer. 



/ -^ 2 







Phil. Soc, Phila., 1889, p. 454, fig. 23, 1, dorsal view ; fig. 2, 

 side view; fig. 3 iront view; ^g. 4 dorsal view of another 

 specimen. Species based on Randall's specimen 9504 A, of 

 his collections near Warren, Pa. 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 

 posterior side from two-thirds to four-fifths that of the anterior ; 

 both sides convex ; on the anterior side there is a prominent sub- 

 angular elevation, commencing at the apex and continuing to the 

 base ; on each side of the carina a slight depression ; other por- 

 tions of the shell without plications or elevations. Aperture 

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

 Sufrace marked by elongate pustules, subregularly arranged, 

 giving to the surface the appearance of being coarsely striated, 

 three in the space of 5 mm. There 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 charac- 

 teristics of this species are the short conical form, the rapid en- 

 largement from the apex to the base, and the elongate pustules 

 of the surface. From those species having a carina it is dis- 

 tingushed as follows : from Platycerus carinatum by its 

 conical form, the straight apex, the absence of plications and 

 the non-sinuosity of the peristome ; from Platyceras mitelli- 

 form by its larger size, conical form and the ornamentation 

 of the surface ; from Platyceras conicum by its shorter form 

 and the abserzce of conspicuous plications and the consequent 

 non-sinuosity of the peristome. It most closely resembles 

 Platyceras dor sale of this formation, 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 



