458 NON-MARINE FOSSIL MOLLUSCA. 



The next species that are to be mentioned in the order of geological 

 time are two that were discovered by Mr. Meek in the estuary deposit 

 at Coalville, Utah, which has already been several times mentioned. 

 One of these species was described by him under the name of Neritina 

 bannisterij* and is represented on Plate 5. It is closely allied with the 

 foregoing Jurassic species, and specimens of both have been found 

 which still show the original color-markings of the surface. Neritina 

 bannisteri has also a near ally in N. incompta White, from the marine Cre- 

 taceous strata of the same epoch, and which is found in the same region. 

 Indeed, it is not improbable that these two forms are only varieties 

 of one and the same species. If so, the fact implies that the species 

 ranged from marine into brackish waters, with no more than a varietal 

 change as a consequence. 



Associated with this typical Neritina in the Cretaceous estuary de- 

 posit at Coalville is a species which Mr. Meek described under the 

 name of N. bellatula; and with it, also, another form, which he named 

 N. carditoidesA The type specimen of the latter is very imperfect 5 but, 

 judging from the characters which it shows, it is thought to be identical 

 with N. bellatula. Both the forms are represented on Plate 5. 



These two last-named forms of Neritina belong to a subordinate type 

 to which Mr. Meek gave the subgeneric name of Velatella. The type is 

 an extinct one, as has already been intimated, and is at present known 

 only in Cretaceous and Laramie strata.J 



In the Bear Eiver Laramie beds a very small species occurs, which I 

 have described under the name of Neritina naticiformis.% It apparently 

 belongs to the typical section of the genus. It is represented on Plate 7. 



The Laramie species belonging to the subgenus Velatella, which has 

 been referred to, was first discovered at Black Buttes Station, in South- 

 ern Wyoming, and described by me under the name of N. ( V.) baptista. \\ 

 Numerous specimens of it have since been discovered in the Laramie 

 strata east of the Rocky Mountains in Colorado, all of which, including 

 the type specimens, have preserved upon their surface the original color 

 markings with which they were ornamented while living, and which are 

 represented by Figs. 16-20 on Plate 23. 



Associated with N. ( V.} baptista, at the Wyoming locality, is the form 

 which I have described under the name of Neritina volvilincata^ and 

 which is illustrated on Plate 23. The type specimens were found in 

 Southern Wyoming and Northwestern Colorado, none of which showed 



*An. Rep. U. S. Geol. Sur. Terr, for 1878, Part I, p. 25, pi. 12, fig. 10. 



tFor descriptions and figures of these two forms, see An. Rep. U. S. Geol. Sur. Terr, 

 for 1878, Part I, pp. 27, 28, pi. 12, figs. 7 and 8. 



t For a diagnosis of this subgenus, see An. Rep. U. S. Geol. Sur. Terr, for 1878, Part 

 I, p. 27. 



$An. Rep. U. S. Geol. Sur. Terr, for 1878, Part I, p. 89, pi. 30, fig. 3. 



|| An. Rep. U. S. Geol. Sur. Terr, for 1878, Part I, p. 89, pi. 29, fig. 6. 



11 An. Rep. U. S. Geol. Sur. Terr, for 1878, Part I, p. 88, pi. 21, fig. 6. 



