INSTITUTE OF SCIENCE, PHILADELPHIA. 277 



more extended comparative study than they have received, but it cannot be 

 attempted here. I may observe, however, that, in sorting over large numbers 

 of specimens of one species, either recent or fossil, it will be noticed that 

 there are two sets as it were, otherwise similar, one much more slender than 

 the other. This may be a sexual difference ; it is observable in Bittium and 

 Sella also. The principal variations of the species are : ist, size, there being 

 in almost any large lot a few or possibly many dwarfs, otherwise similar — re- 

 calling the difference of size in Cyprcsa ; 2d, in the intensification of (a) the 

 transverse wavy sculpture, which in any species which has it may be strong, 

 weak or wholly absent ; {b) the nodulations or tessellations of the primary 

 spiral bands or revolving ridges, which vary in the same species from obso- 

 lete to very sharp and prominent ; [c] the prominence of the primary bands, 

 which is very variable, apart from the nodules they may bear. The secondary 

 fine striation, as in Biicclnnm, is much more constant in its features than the 

 coarser sculpture. 



The scarcity of Cerites in the American Tertiary has been noted as a 

 characteristic of the fauna, but this is due rather to our ignorance of the Terti- 

 ary faunae of North America than to a real absence of species of Cerlthlum. 

 Some enormous species are found in the early Eocene Prairie Creek beds, but 

 they are badly preserved and have only lately been recognized as Cerites. It 

 is probable, however, that no such thick beds of species of this genus as are 

 found in exotic Eocene strata occur in the American Tertiary. 



Quite a number of fossils have been referred to Cerlthlum in the Ameri- 

 can faunee which appear to belong elsewhere. Thus Cerlthlum {Cerlthlded) 

 agnotuvi and C. persum de Greg., C. stiiatiiin Lea and its synon3'mous Proto 

 vctiista Conrad, are not Cerites, but are apparently species of Pseudomelanla. 

 C. dlslocatum Say and C. carollnensls and iinlllneatiini Conrad should be re- 

 ferred to Terebra. C. Fremontl, nodulosiini and tenenim Hall, from brackish- 

 water-beds of the West, collected on Fremont's expedition, are Melanians of 

 the genus Gonlobasls, as is probably Cerlthlum texmmni Heilprin. 



To the Melanians also must be referred the Compsophntra trlnodosa 

 {= Scalarla trlgemmata Conr.) of Conrad, which is a Gonlobasls and has noth- 

 ing to do with Scala. 



To Cerlihldea proper must be referred C. callfornlcum Haldeman and C. 

 sacratum Gould of California. C. mlsgtnn de Greg, from Claiborne is a frag- 

 ment of an Asiyrls, and C. mlturum of the same author the tip of an AnacJils. 

 C. Incrosjim de Gregorio is regarded by that author as identical with C. agno- 

 tiim. C. dadaleum H. C. Lea is a Turbonilla; C. declsum and mediate of 

 Conrad, miserable fragments which that writer afterward referred to Fiisiis ; 

 C. slllceum Conrad is doubtfully referable to Cerlthlum, and C sageimla Con- 

 rad (in Morton's Synopsis, App.) is a list-name for which no figure or descrip- 

 tion is extant. Cerlthlum corjiutum Heilprin is a Pyrazlslnus. 



A group of very interesting species which can hardly be said to be 



