WHITE.] ANNOTATED CATALOGUE. 455 



affinities ; but it is at present left with the Helicidae, where those au- 

 thors placed it. 



Professor Powell obtained from the Bitter Creek Group, in Central 

 Utah, the earliest of the fresh- water Eocene series, a species which I 

 described under the name Helix peripheria,* and which appears to pos- 

 sess the subgeneric characteristics of Aglaia Albers. From the Eocene 

 Green Eiver Group of Southern Wyoming he also obtained H:riparia\ 

 White, which is apparently referable to the subgenus Arianta Leach. 

 Both the last-mentioned species are figured on Plate 29. 



Whether Helix Jcanabensis, H. sepulta, H. evanstonensis, H. peripJieria, 

 and H. riparia are correctly referred to the respective subgenera in con- 

 nection with which they have just been mentioned, or not, their diversity 

 of form gives sufficient indication that the Helicida3 had become widely 

 differentiated during those early epochs in which they lived, probably 

 quite as widely as their living representatives are, and under closely 

 similar forms. 



At present, the only known Miocene species of Helix is H. leidyi Hall 

 & Meek; which is also the only known fossil species of that genus of 

 later date than the Eocene. It is represented on Plate 32. 



PUPUXE. 



If it were not that the existence of a diversified land molluscan fauna 

 during the Coal-Measure period is a well-established fact, we should be 

 slow to accept the conclusion of Dr. Dawson that the shell which he 

 has described from the Erian (Devonian) plant-beds of St. Johns, New 

 Brunswick, under the name of Str ophites granclceva is really a land 

 snail. In view of the fact just stated, and of the reasons which he gives 

 for his conclusions, we seem to have no reason to doubt that the shell in 

 question is, as he suggests, closely related to Pupa. A copy of his figure 

 of it is given on Plate 1. 



Although an unexpectedly large number of species of non-marine 

 mollusca has been obtained from strata so ancient as those of the Coal- 

 Measures, the fact that the Gasteropoda are all land snails shows clearly 

 that the complete non-marine mollusca of that period is very far from 

 being fully known. It cannot be supposed that coordinate families, 

 similar to those with which representatives of the species referred to are 

 raneously with those ancient species which have been discovered. The 

 known to have been afterwards associated, did not exist contempo- 

 continental area, however, having been at that time smaller than it 

 afterward became, the rivers were necessarily comparatively few and 

 small. Therefore, the fresh-water mollusca, as compared with those of 

 the land, were perhaps proportionally fewer then. 



* Powell's Rep. Geology Uinta Mountains, p. 130. 

 t/Wd. 



I See mention of some California species of Helicidso found in a fossilized condition* 

 under-thc head of spurious and doubtful species, on a following page. 

 Ain. Jour. Sci., vol. xx (3), p. 413. 



