WHITE.] ANNOTATED CATALOGUE. 451 



were described by Meek & Hayden, under the names respectively of 

 B. longiusculus and B. rhomboideus,* both of which are represented on 

 Plate 25. These two forms are so closely like Physa that they may 

 apparently be with equal propriety referred to that genus. Indeed if 

 these two species are properly referred to BuUnus, then Physa bridger- 

 ensis and one or two other species herein referred to Physa ought to be 

 referred to Bulinus also. 



In the Laramie strata, east of the Rocky Mountains, in Colorado, Bu- 

 linus disjunctus White,! occurs. It is represented on Plate 25. 



Another Laramie species was discovered in Southern Utah by Pro- 

 fessor Powell, which I described under the name of Physa kanabensis, { 

 but which ought to be referred to Bulinus. This species is yet known 

 only by specimens that are too imperfect for satisfactory illustration. 



ANCYLID.E. 



The Ancylidoe, when present, always form an inconspicuous feature 

 in any fresh-water fauna, and the family is represented by only two 

 published species, so far as is now known, in all the North American 

 strata. One of these species, Acroloxus minutus, Meek & Hayden, was 

 obtained by them from the Laramie strata near Fort Union, in the Up- 

 per Missouri Eiver region. It is illustrated on Plate 24. 



The other fossil representative of the family is Ancylus undulatus, 

 Meek, 1 1 from the Miocene deposit of the Kawsoh Mountains of Northern 

 Nevada, where it was found associated with the two species of Curinifex 

 that have already been mentioned, and also with certain other fresh- 

 water forms. It is represented on Plate 32. 



In the Southern Idaho equivalent of the Eocene beds just mentioned, 

 associated with Melania taylori, Lithasia antiqua, Sphcerium rugosunij 

 &c., an interesting shell has been found which seems to agree with the 

 genus Latia Gray, although that genus has hitherto been known only 

 in certain portions of Oceanica, and only in the living state. 



This form may be briefly characterized as follows : 



Latia dallii (sp. nov.), plate 32, figures 37, 38, 39, and 40. Shell sub- 

 ovate in marginal outline 5 irregularly convex above ; the posterior por- 

 tion narrowing rapidly to a small prominent umbo, which ends in a 

 very small, closely-incurved beak; the beak turned a little to the right 

 side, and making about one full volution; semilunar shelf or septum 

 comparatively large. Surface marked by many strong, irregular, con- 

 centric undulations ; but otherwise it is comparatively smooth, being 

 marked only by fine lines of growth. 



*U. S. Geol. Sur. Terr., vol. ix, pp. 541,542, pi. 43, figs. 16 and 17. 



t An. Rep. U. S. Geol. Sur. Terr, for 1878, Part I, p. 86, pi. 24, fig. 6. 



t Powell's Rep. Geology of the Uinta Mountains, p. 119. 



U. S. Geol. Sur. Terr., vol. ix, p. 543, pi. 44, fig. 10. 



|| U. S. Geol. Sur. 40tli Parallel, vol. iv, p. 188, pi. xvil, fig. 12. 



