300 A MANUAL OF AMERICAN LAND SHELLS. 



eter, 35"""), furuisbed with a strong, tooth-like prominence on the per- 

 istome, near its cokimella extremity. There is a variety, quite common 

 among the Pennsylvania mountains, characterized by a strong parietal 

 denticle. It is already mentioned above. It might readily be con- 

 founded with ex'olctt(s,hnt wants the more ventricose body- whorl of the 

 latter, and differs widely in its genitalia (see Fig. 320). 



It occurs fossil in the Post-Pliocene. From Natchez Bluff I have 

 specimens with a remarkably flattened spire. 



A reversed individual has been noticed. 



Animal varying from pure white and cream-color, through various 

 shades of gray, to blackish j upper part of head and neck slightly 

 brownish ; extremities of eye-peduncles smoky ; eyes black. Eye- 

 peduncles more than 12""° ia length when fully extended, slender and 

 cylindrical. Foot with a slightly expanded margin, terminating pos- 

 teriorly in an acute angle. Glandular tubercles very distinct and 

 prominent, on the back arranged longitudinally, on the eye-peduncles 

 long and narrow. Extreme length, 62""", (See Terr. Moll., Ill, Plate 

 II.) 



The animal deposits about fifty eggs at each laying, which is repeated 

 one or more times during the season. The eggs are three sixteenths of 

 an inch in their greatest diameter, and covered with minute points. 

 The last laying is often delayed to so late a period of the year that the 

 earth is covered with snow before they are hatched. The develoi)ment 

 of the embryo is then suspended until the next spring. When newly 

 excluded from the egg the shell consists of one whorl and a half, the 

 length of its column or axis being about one-eighth of an inch, and its 

 breadth somewhat less. No umbilicus is then discernible. I have not 

 been able to determine how much time is required to complete its 

 growth, but I am induced to believe that the peristome, the evidence 

 of maturity, is added in the second year. 



The jaw is arcuate, of uniform breadth throughout ; ends blunt, 

 smooth on their anterior surface, the balance of the jaw with 10 stout 

 ribs, denticulating either margin. 



Outer laterals of the lingual membrane have distinct side cusps, as 

 well as cutting points. Teeth 44-1-44, with about 12 laterals. (Terr. 

 Moll., V, Plate VIII, Fig. K.) 



Genitalia, as well as complete anatomy, figured by Leidy, I. c. The 

 penis sac is stout, rather short, cylindrical, with a median prepuce {h) ; 

 it receiv^es the vas deferens at its summit ; the retractor muscle is 



