white.] ANNOTATED CATALOGUE. 55 



with the latter family. It is the only known species of the genus 

 which has been proposed to receive it, either fossil or living.* 



From the fresh-water Miocene deposits, which have already been men- 

 tioned as occurring- in Sou them Idaho and in the vicinity of the Kawsoh 

 Mountains, Mr. Meek described two forms and Mr. Gabb another, which 

 they referred to Melania, Mr. Meek doing so with an expression of doubt 

 but Mr. Gabb with none. Copies of their origin al figures of these forms 

 are given on Plate 32. 



Mr. Meek gave the names M.9 sculptilis and M.f sahsculptilisj to his 

 two species, and Mr. Gabb, that of M. taylori\ to the one he described. 

 Conrad's M. decursq is probably a synonym of the latter. 



All three of these forms belong to one and the same type, and per- 

 haps represent only one species. This type differs considerably from 

 the other types that have herein been referred to the Melaniadte. The 

 species belong to a fauna from which, as before stated, no genetic lines 

 seem to have reached the present Mississippi drainage system, and, like 

 a portion of their associates, are quite unlike any other North American 

 species, either living or fossil. All the known species of that fauna are 

 herein referred to and figured, but, for the purpose of separate view, 

 their names are given, as follows: Melania? sculptilis, M.f subsculp- 

 tilis, M. ? taylori, Lithasia antiqua, Cqrinifex, ( Yorticifex) tryoni, G. ( V. ) 

 binneyi, Ancylus undulatus, Sphcerium rugosvm, and & f idahoense. 



The genus Melanopsis Lamarck is not known among the living mol- 

 lusca of North America, and until very lately it was believed to be also 

 absent from all North American strata. A small shell from the Lara- 

 mie strata east of the Eocky Mountains in Colorado, associated with 

 Corbicula, Gorbula, Melania, Neritina, Anomia and Ostrea, is here de- 

 scribed for the first time, and referred provisionally to Melanopsis. Jt is 

 evidently congeneric with the living Melanopsis costellata Ferussac, and 

 also with the Eocene M. buccinoidea Ferussac; both from Western Europe. 



Melanopsis f americana (sp. nov.), Plate 23, Figs. 21, 22, and 23. 



Shell very small, sides straight, and meeting at the apex at an acute 

 angle; volutions six or seven, those of the spire not convex, but so flat- 

 tened as to show only a linear suture between them, which is somewhat 

 irregular; proximal portion of the last volution gently convex,its length 

 being more than half the entire length of the shell; outer lip thin, not 

 expanded, its margin not distinctly sinuous; inner lip having a very 

 strong callous nearly filling the distal end of the aperture, leaving a nar- 

 row groove between it and the margin of the outer lip, and gradually 

 diminishing in thickness towards the proximal end of the aperture; 

 aperture, as bounded by the outer lip and callous inner lip, rudely sub- 



* See foot-note on page 58. 



tU. S. Geol. Sur. 40th Parallel, pp. 195, 196, pi. 17, figs. 8 and 9. 



X Paleonotology of California, vol. ii, p. 13, pi. 2, fig. 21. 



