4G4 NON-MARINE FOSSIL MOLLUSCA. 



which I have given the generic name of Cassiopclla,* describing the 

 species under the name of C. turricula. It is figured on Plate 23. Like 

 Pyrgulifera,) it is the sole representative of an extinct generic type.t It 

 is umbilicate, and in this respect differs from any other shell that 

 has been referred to the Ceriphasiidse. It is referred to that family 

 only provisionally, and because there appears to be equal or greater 

 objections to referring it to any other established family. It is so 

 referred mainly because of its agreement in form, and the character of 

 its outer and inner lips. 



Passing now to the three groups of fresh- water Eocene strata, the 

 Wahsatch, Green Biver, and Bridger groups, as they are developed in 

 Wyoming, Colorado, and Utah, we find that the genus Goniobasis con- 

 stitutes even a more conspicuous feature of the faun of those groups, 

 as regards proportionate numbers of individuals, than it did in the 

 Laramie period, although the number of species was so much greater 

 then. Notwithstanding this great generic prominence, and also the fact 

 that four species have been described by different authors from those 

 fresh- water Eocene groups under the name of Goniobasis^ I am not 

 at present prepared to admit that more than one well-defined species has 

 yet been found in any of the strata of those three groups. Taking this 

 view, we must of course regard those forms which have been described 

 as separate species, as only varieties of the first one described ; although 

 it cannot be denied .that th covariation is, in some cases, very consider- 

 able 5 and if intermediate forms had not been discovered, their specific 

 separation would never have been called in question . In this view of the 

 case I have selected tenera Hall as the specific name by which to desig- 

 nate this variable and abundant Eocene species of Goniobasis, because 

 it was the first specific name that was applied to it by any author. It 

 will be convenient and proper, however, to retain the other names as 

 those of varieties, or even in some sense as species. For the same pur- 

 pose I propose the name Goniobasis columinis for the extravagantly orna- 

 mtented forms represented by Figs. 29 and 30 on Plate 31. A consider- 

 able series of these forms from different localities in those fresh-water 

 Tertiary groups is given on Plate 31, which shows the wide range of 

 variation and the transition of the forms and the character of their 

 ornamentation. 



For diagnosis of this^genus and description and figures of tho species, see An. Rep. 

 U. S. Geol. Sur. Terr, for 1878, part I, pp. 66, 67, pi. 27, fig. 3. 



t Since these paragraphs were written, Mr. Edgar A. Smith has published, in the 

 Proceedings of the Zoological Society of London, two species under the new generic 

 name of Paramelania, found living in Lake Tanganyika, in Africa, which seem to bo 

 congeneric with Pyrgulifera. 



t These proposed species are respectively as follows : Goniobasis tenera ( = Cerithium 

 tenerum Hall), Fremont's Rep. Oregon & N. California, p. 308, pi. Ill, fig. 6 ; G. simpsoni 

 Meek, Simpson's Rep. Great Basin Utah, p. 365, pi. v, iig. 1 ; G. nodulifcra Meek ( = Ceri- 

 thium nodulosum Hall, Fremont, op. cit.), and G. carteri Conrad, Am. Jour. Conch., vol. 

 iv, p. 280, pi. 18, figs. 6 ami 7. 



