EAflTESN PROVINCE INTERIOR REGION SPECIES. 



257 



s&^ 



r. allcrnatrt, 

 caiiiKited. 



P. altei nata, 

 vai. mordax ? 



Flo. 272. 



The variation of color ranges from pale straw to dark reddish-brown, 

 in each extreme being sometimes uniform. In outline the 

 variation ranges from depressed to A^ery globose. In 

 sculpturing it varies greatly. A compara- fig. 271. 

 fiveiy smooth variety, with a shining, some- 

 what translucent epidermis, has been noticed 

 in ISTew York by Mr. Bland, under the name 

 of vi\i\ Fergusoni. A form with stronger stria^ 

 and well-developed carina is figured in Fig. 

 270, The coarsely striated form, which I pre- 

 sinne to be II. mordax, is figured also (Fig. 

 271). This is considered by Mr. Bland to be 

 a \ ariety of Cumherlandiana. I have received 

 it from Eastern Tennessee and Virginia. I 

 have also given a figure (Fig. 272) of the magnified surface 

 of a strongly ribbed form from North Carolina, and a view (Fig. 273) 

 of a strongly ribbed form from the Post-Pliocene. 



In New England this is perhaps the most common species of the 

 genus. It abounds in the forests, and is not uncommon in 

 the open country in moist situations, where it can find shel- 

 ter under logs and stumps. It seems to be more gregarious 

 than other species; at any rate, numbers are more fre- 

 quently found in the same retreat. It does not bear a 

 change from a moist to a dry situation so well as many other species. 

 In captivity it remains buried a great part of the time under the moist 

 earth, with the body half protruded. If removed to the fig. 273. 

 surface, it withdraws within the shell, protects its orifice 

 by three or four coverings, and soon dies unless supplied ^^r^ 

 with moisture. _ WiMiM. 



The foot of the animal is smaller and the eye-peduncles 



r. alternata, 



shorter than in either of the other species possessing so f°^**ii- 



large a shell ; it is also flatter and thinner. The mantle is deeply 

 tinged with the coloring matter which ornaments the shell, and which 

 is sometimes secreted in such profusion as to give a saffron tinge to the 

 trace which it leaves on objects over which it crawls. It is distributed 

 over the animal, and arranged in minute points, which are most thickly 

 clustered on the margin and on the glandular tubercles of the surface. 

 There is a reversed specimen in the Museum of Comparative Zoology 

 at Cambridge. 



1749— Bull. 28 17 



Surface of 

 P. alternata. 



