MUSEUM OF COMPARATIVE ZOOLOGY. 209 



may be said to inhabit the whole continent of North America as far 

 south as Mexico. The range of some is still greater. Thus, Zonites 

 minusculus has been found from British Columbia to Labrador on the 

 north to Yucatan and Florida on the south, and still farther in Cuba, 

 Jamaica, Porto Rico, and Bermuda. .Helix labyrinthica also is found 

 over all Eastern North America, and perhaps in Mexico (as H. Strebeli, 

 see Fischer and Crosse, Moll. Mex. et Guat., 267). It is also by some 

 considered identical with an Eocene fossil of France and England. 

 (See Land and Fr,esh\v. Shells N. A., I. 84.) Zonites arboreus ranges 

 from Labrador to New Mexico, and in Nevada and California, and 

 from British Columbia to Florida, Cuba, and Guadaloupe. Vertigo 

 ovata is found from Maine to Mexico and in Cuba. 



The character of the soil and climate, with, perhaps, the gradual ele- 

 vation, is such as to render the land shells rare, if not quite extinct, 

 before the Rocky Mountains are reached, the western boundary of the 

 Interior Region. But one species, Patula solitaria, seems to have 

 passed this mountain-barrier into the Central Province. This is found 

 with P. Cooperi in Montana and Idaho, very difficult to distinguish 

 from forms of the last species. It is, however, oyiparous (from Salmon 

 River, Idaho),, while P. strigosa, Cooperi, Hemphilli, and Idahoensis 

 are viviparous. It has been suggested by Dr. H. Dohrn that this 

 characteristic is connected with the fact of the great dryness of the 

 soil in the Central Province. The young shell is ready to protect itself 

 from the moment of its birth, while, if deposited as an egg by the parent, 

 it might perish from drought. 



The following list contains the names of all the species inhabiting the 

 Interior Region, including those which have spread into it from the 

 Northern Region : — 



Macrocyclis concava. Zonites indentatus. 



Zonites fuliginosus. limatulus. 



friabilis. minuscules. 



laevigatus. fulvus. 



ligerus. gularis. 



intertextus. suppressus. 



inornatus. internus. 



nitidus. Limax campestris. 



arboreus. Patula solitaria. 



viridulus. alternata. 



VOL. III. 14 



