1896.] 



NATURAL SCIENCES OF PHILADELPHIA. 



317 



the confused masses and ducts of the generative and digestive 

 tracts, shown crowded together. It appears, however, that the long 

 sperraatheca duct bears a diverticulum, and the vas deferens is of 

 unusual length. Maynard does not seem to have been fortunate 

 in his preparations, and his figures afford no data of assistance to us. 

 The only species seen by us in the flesh is Cerion Yumaense P. & 

 V. ;* the specimens examined being part of the type lot received from 

 Mr. Henry Prime and corresponding to fig. 3 of pi. XI. 



The penis (p) is a moderately stout sack from the termination of 

 which the short retractor springs. Near the base of the penis the 

 vas deferens (c. d.) enters ; and this is of extraordi- 

 nary length as shown in the figure. The spermatheca 

 (sp.) has a long duct, without branch or diverticulum ; 

 and there is a large talon (t). Ovotestis not ob- 

 served. 



A transverse section of penis-sack some distance 

 above entrance of vas deferens shows a cavity with 

 bipartite or dumb-bell shaped section, filled with a 

 granular yellowish substance. 



It will be seen that this diflPers from Leidy's figure 

 in lacking the diverticulum of the spermatheca duct. 

 It agrees with it in showing a7i excessively long free 

 portion of the vas deferens, inserted abnormally low on 

 the penis ; and these will doubtless prove to be generic 

 characters widely sundering Cerion from all other 

 genera of which the genitalia are now known. 



Subdivision of the Genus Cerion. 



Four groups of subgeneric value may be distinguished by concho- 

 logical characters. Stropihiops only is known anatomically. 



I. Axial and parietal folds wanting, Eostrophia. 



II. Axial fold in angle at root of columella ; no parietal fold, 



Cerion s. str. 



III. Axial and parietal folds present, the latter near middle of 

 parietal wall, single and short, not over one-third of a whorl 

 long, Strophiops. 



IV. Axial and parietal folds present, the latter very long and 

 doubled, or short and interrupted, with an accessory denticle; 

 rarely obsolete, Diacerion. 



* The dissections and drawing are by Mr. Vanatta. 



C Yumaense 

 P. &V. 



