176 CEKION. 



scribed a large number of most interesting species and varieties, so 

 that His work on this genus has been an important one. However, 

 he has unduly multiplied species and sub-species, basing them on 

 characters we hold to be too slight and inconstant, and his work is 

 marred by inaccuracies of all kinds. 



In 1896, Mr. Vanatta and the writer published a catalogue of the 

 genus, embodying the results of both biologic and synonymic study. 

 This catalogue has served as a basis for the present monograph, 

 although further study with more material has modified some of the 

 conclusions then reached, and has resulted in a grouping of the spe- 

 cies believed to be more natural. 



The more striking peculiarities of Cerion, besides the pupiform, 

 compact and calcareous shell, are (1) the low entrance of the epi- 

 phallus into the penis, a feature I do not remember noticing in any 

 other genus; (2) the excessively long free vas deferens ; (3) the 

 diverticulum of the spermathecal duct (occurring also in Helix, 

 Buli-minus, Clausilia); (4) the rather short, oblong kidney, with very 

 extensive lumen. 



The external anatomy, teeth, jaw, and most other details present 

 nothing unusual in ground-snails of the Holopod group. 



Cerion has been associated with the Pupidce by most authors, but 

 there is little in the anatomy to justify such an association, while the 

 pallial organs and genitalia show it to belong to a widely different 

 group. 



General Anatomy of Cerion. 



The lung in C. mumia chrysalis is about three times as long as 

 wide, traversed along the middle by a large pulmonary vein, with no 

 large branches, the reticulation being quite invisible in an unstained, 

 non-injected preparation. The kidney is about double the length of 

 the pericardium, and has a very large cavity. The secondary 

 ureter is not noticeably differentiated (pi. 47, fig. 30). In C.incana 

 Leidy distinctly figured a branching reticulation of the lung anteriorly, 

 and a secondary ureter ; whether correctly or not, only additional 

 examination will show. 



The radula is normal in shape ; teeth 27, 1, 27 in C. m. chrysalis 

 and (?. incanum, 30, 1, 30 in C. regium and C. abacoense. The 

 central tooth is rather wide, the length of the basal plate sometimes 

 exceeding, sometimes surpassed by the median cusp; side cusps well 

 developed. The laterals have a long inner cusp, bifid beyond the 



