2P8 A MANUAL OF AMERICAN LAND SHELLS. 



icus. The color of the epidermis is generally much darker. The only 

 considerable variation in the characters of the shell is caused hj the 

 depression of the spire in some individuals, and indeed in all speci- 

 mens from certain localities. In its most perfect condition it is often 

 subconical. It is subject to some irregularities in the form of the aper- 

 ture, and there is sometimes an indication of pale bands in the epi- 

 dermis of the body-whorl. 



A large individual had the greater diameter 48, lesser 40"""; height, 

 30mm^ 



Animal: Head, upper part of neck, tentacles, and eye-peduncles fer- 

 ruginous; eyes black; foot rusty, the sides more or less shaded with 

 blue by the fluids of the animal, which are visible through its semi- 

 transparent substance. Eye-peduncles shoit, in proportion to the size 

 of the animal, and robust, their situation, when retracted, marked by 

 brown lines. Foot large and thick. Genital orifice indicated by a 

 slight prominence. Superficial glands large and distinct. On the cen- 

 ter of the back is a line of them, of an oblong narrow shape, with a 

 furrow on each side ; those on the sides and posterior part of the foot, 

 when examined b}' a microscope, exhibit numerous subcutaneous white 

 dots or points, arranged in clusters. Length equaling twice the 

 diameter of the shell (see Bost. Journ. N. H., I, Plate 1). 



Jaw and lingual membrane as in albolabris. Terr. Moll., V, Plate 

 VIII, Fig. G, shows the membrane. 



Genitalia also same as in- aliolabr is (see Proc. Phila. Ac. Nat. Soc, 

 1876, 189, Plate VI, Fig. 1). 



I still retain as a distinct species the form known as major, though 

 the study of the limits of variation in the shells of our species has led 

 me strongly to doubt its specific value. I am inclined to consider it as 

 a greatly developed form of albolabris, caused by certain peculiarly 

 favorable local causes in a certain portion of the Southern Eegion. 



See also concluding remarks under Mesodon Andrewsi. 



ITIesodon aUbolabris, Say. 



Shell imperforate, convex; epidermis immaculate, of a uniform 

 ^"■^'"- yellowish-brown russet or light chestnut-color; 



whorls 5-G, with fine parallel striae running ob- 

 liquely across them, and spirally striated with 

 very minute and delicate, but distinct, wavy, 

 imi)ressed lines, which are most apparent on the 

 M. albolabris. h:»<'l^ of thc reflected peristome; suture well 



