MUSEUM OF COMPARATIVE ZOOLOGY. 201 



Several of the above will eventually prove to be synonymes, but the 

 total number of species is small in comparison with the great size* 

 of the Pacific Province. An equal extent of territory in the Mis- 

 sissippi Valley, or even on the Atlantic coast, would show a larger 

 number ; and the comparatively small regions of Texas, Florida, and 

 the Cumberland Mountains would each show an equal number of 

 species peculiar to itself, independent of what they have in common 

 with the rest of Eastern North America. This disparity in number is 

 still more plainly shown in the separate region of Oregon. Thus it ap- 

 pears that the Pacific Province is not rich in the number of its species, 

 but it is peculiarly favored in their size and beauty, — in this respect 

 strikingly in contrast with the Central Province and Eastern Province. 



From the Central Province the Pacific Province is quite distinct. A 

 few species have been shown above to inhabit both slopes of the Sierra 

 Nevada, and a few of the Oregon species have passed the barrier of the 

 Cascade Mountains on the north, but the peculiar Pacific forms, such 

 as Arlonta and Aglaia, are unknown in the Central Province. On the 

 other hand, the only form which has any development in the Central 

 Province, Palula, is scarcely known in tile Pacific Province. 



Compared with Eastern North America, or the Eastern Province, as 

 it is designated below, the Pacific Province is remarkable for the absence 

 of all the larger Zonites. The presence of the smaller species, also, may 

 perhaps be accounted for by migration from the north, so that the genus 

 Zonites cannot be considered as characteristic of the Province. The 

 genus Pupa is less common. The genera Tebennophorus and Pallifera, 

 so universally distributed in Eastern North America, are unknown, and so 

 are the southern genera Glandina, and Bulimulus. On the other hand, 

 we find the genus Macrocyclis much more developed, and meet several 

 genera unknown in the Eastern Province, such as Ariolimax, Binneia, 

 Prophysaon, and Hemphillia. The genus Helix is proportionally more 

 developed in the Pacific Region, and is represented by quite dissimilar 

 subgenera. The sections so peculiar to the Eastern Province, Polygyra, 

 Stenotrema, Triodopsis, Mesodon, are scarcely represented. In their 

 place we find Aglaia and Arionta, forms unknown in the Eastern Prov- 

 ince. The latter, though feebly represented in Europe, is the form of 

 Helix characteristic of California. It is prolific of species and also of 

 varieties to a degree which has caused some confusion in the synonymy. 

 The section to which Helix Newberryana belongs, Glyptostoma, is also 

 peculiar to California. 



