16 Trans. Acad, Sci. of St. Louis. 



radiating costae, and ^ye or six oblique spines upon each side 

 of the beak. The descriptions of O. illinoisensis do not 

 state how many more than 120 costae there may be in that 

 species, but some specimens which have been observed from 

 the Osage fauna, are certainly G. illinoisensis, and they pos- 

 sess as many as 200 costae, so that the number of costae can- 

 not be taken as a good character for the separation of the 

 two species. The cardinal spines, however, might well 

 furnish a distinguishing character if it could be observed, but 

 unfortunately, in the majority of cases the spines are not pre- 

 served in specimens of Chonetes. Furthermore, the number 

 and direction of the cardinal spines is a character in which one 

 may be easily mistaken unless it be observed in a considerable 

 number of specimens. Therefore, in consideration of the 

 facts that C muliicosta has never been illustrated, and that 

 apparently no one except the author of the species has ever 

 been able to identify it, it seems best to consider the two 

 species C. illinoisensis and C, muliicosta as synonyms. It is 

 possible, of course, that at some future time, when Win- 

 ch ell's types are illustrated, the two species will be shown 

 to be distinct, but the short description of C. muliicosta 

 which has been published, is not sufficient to make this at all 

 certain. 



A shell which is referred to C . illinoisensis is a common 

 species in the Northview fauna. None of the specimens 

 have the cardinal spines preserved, and the number of radi- 

 ating costae is from 150-175. In general form and size 

 they are not different from the specimens of O. illinoisensis 

 which are so abundant in the Osage fauna, but they are 

 usually much flattened by pressure. 



Chonetes sp. — Cf. C. tumidus Herrick. 



Besides the specimens referred to Chonetes illinoisensis y 

 there are in the Northview fauna several specimens of an- 

 other species of the same genus. These differ from the 

 former in their smaller size, their highly convex pedicle 

 valves, their coarser and smaller number of radiating plica- 

 tions, and their more extended hinge-line. Only a few speci- 

 mens have been observed, and these are all of them more or 



