white.1 CRETACEOUS FOSSILS OF COALVJLLE, UTAH. 237 



remarkably modern in type, and, seen separately, and without any knowl- 

 edge to the contrary, no paleontologist would be warranted in referring 

 them to an earlier period than the Tertiary. 



The evidence of their Cretaceous age, however, is unquestionable, 

 there being more than 1,000 feet in thickness of marine Cretaceous strata 

 resting upon them ; and more than an equal thickness of Cretaceous 

 strata lies beneath them. 



30. Pliysa carletonl Meek. 



The figure of this species in another part of this volume shows plainly 

 its modern type. For further remarks concerning it and its associates, 

 see No. 29. 



31. Pliysa f 



This is possibly identical with P. carletonl. See a figure of it in another 

 part of this volume ; and also remarks under No. 29. 



32. Neritina bannisteri Meek. 



This is apparently a typical Neritina. See under No. 29 for general 

 remarks upon its associates. 



33. Neritina pisum Meek. 



This is very like the next following species, but it is probably distinct. 

 It is from a calcareous sandstone layer in the first ridge of Mr. Meek's 

 .section, associated with Nos. 31, 37, 38, and other species. Although it 

 is of the same type as No. 32, its associates are all marine forms. 



34. Neritina piriformis Meek. 

 See remarks under No. 33. 



35. Neritina ( Yelatella) bellatula Meek. 



Mr. Meek discovered this species together with No. 36 in stratum No. 

 10 of his section at Coalville, associated with other brackish- and fresh- 

 water forms. See remarks under No. 29. Together with Nos. 30, 37, and 

 38, it belongs to a section of the genus Neritina, to which Mr. Meek gave 

 the subgeneric name of Yelatella. Some of the associates of Nos. 35 and 

 30 are both brackish- and fresh- water forms, but those of Nos. 37 and 38 

 are all marine forms. The only other known species of this subgenus is 

 N. ( V.) baptista IVhite, from the Laramie strata at Black Buttes Station, 

 where its associates are both fresh- and brackish-water forms. In vol. 

 iv, Expl. & Sur. West of the 100th Merid., I described and figured a 

 form from Cretaceous rocks of Utah, which I referred to N. (V.) carditoi- 

 des Meek, but which possibly belongs to another, but closely allied, spe- 

 cies. Its associates there are understood to be marine forms only. 



30. Neritina (Yelatella) car'ditoidesM.eek. 

 See remarks under Nos. 29 and 35. 



37. Neritina ( Yelatella) patelliformis Meek. 

 See remarks under Nos. 33 and 35. 



38. Neritina ( Yelatella) patelliformis var. weberensis White. 

 See figures and description in another part of this volume. 



39. Euspira coalvillensis White. 



Found only at Coalville and in the first ridge of Mr. Meek's section. 



40. Gyrodcs depressa Meek. 



This well-marked species has been found only in the form of casts, and, 

 so far as I am aware, only from the sandstones of the second ridge of 

 Mr. Meek's section. 



