white.] ANNOTATED CATALOGUE. 43 



type referred to is found among the living mollusca iu Pacific drainage 

 waters, it may be fairly inferred that that Miocene lake was drained 

 into western and not eastern oceanic waters. It should be remarked, 

 however, that no representatives of some of the types which were asso- 

 ciated with those ancient forms of Carinifex are now known to be living. 



PHYSID.JE. 



The Physidaj have been found to be comparatively well represented 

 iu nearly all the strata which have furnished any fossil pulmonate mol- 

 lusca. Both Physa and Buliwiis are represented by several species (all 

 of which are regarded as extinct), ranging from the Cretaceous to the 

 Miocene, inclusive. Notwithstanding their great antiquity, there seems 

 to be among them all very little deviation from the types which are 

 expressed by the numerous living species of those genera. 



The earliest known species referable to the Physidaj is Physa carletoni 

 Meek,* which was obtained by him from the Cretaceous estuary deposit 

 at Coalville, Utah, which has before been referred to in connection with 

 Anomia propatoris, Cyrena carletoni, and Melampttsf antiquus. P. carle- 

 toni is represented by a figure on Plate 5. 



Iu many cases the earliest known species of a genus which is capable 

 of subdivision into subordinate types or sections is not referable to that 

 section which has been selected by naturalists as the typical one; but 

 in the present case Physa carletoni seems to be a typical Physa, while 

 some of the later species seem to depart more from the typical form. 

 These facts are, however, of no great significance, because the section 

 of a genus which is designated as typical is usually only conventionally 

 selected; and, also, because we cannot know with certainty whether the 

 earliest known species was in reality the earliest. Although only the 

 one species just mentioned has yet been discovered in any strata of 

 greater age than those of the Laramie Group (if we except a fragment 

 which has been found in the marine Cretaceous strata at Coalville, Utah, 

 and which was probably drifted to that position from the then adjacent 

 shore t), we cannot doubt that the Physidas were comparatively abun- 

 dant in the Cretaceous period, because that species is so unmistakable 

 in its generic characteristics, and also because it belongs to a type that 

 has reached the present time unchanged. 



An unnamed form, which is probably a true Physa, has been found in 

 the Pear River Laramie beds of Southwestern Wyoming, a figure of 

 which is given on Plate 6.| 



Plate 25 contains figures of a fine large species which Professor 

 Cope obtained from the Judith River Laramie beds in the Upper Mis- 



*An. Rep.U. S. Geol. Sur. Terr, for 1877, p. 30fi, pi. 7, fig. 12. 



t IT. S. Geol. Sur. Terr, for 1877, p. 307, pi. 7, fig. 13. The figure is also given on 

 Plate LXV, accompanying this article. 

 {An. Rep. U. S. Geol. Sur. Terr, for 1878, Part I, p. 85, pi. 30, fig. 11. 



