310 A MANUAL OF AMERICAN LAND SHELLS. 



tootli is wanting there is often a slight deposition of testaceous matter 

 in its place, not distinguishable without close observation. In its 

 genitalia it has decided specific distinction (see albolahris). 



The color of the animal varies in being more or less dark ; but I 

 have never seen an individual which approached the white, pearly, or 

 cream-color which is so common in the animal of M. albolahris. The 

 eggs are white, one-eighth of an inch in diameter, and are laid in the 

 earth, as deep as the body of the animal will extend, in clusters of 

 about twenty. 



There is certainly a strong resemblance between many of our spe- 

 cies, which, with M. albolahris as their type, form a well-marked divis- 

 ion. But as their differences are as constant as their resemblances, 

 it cannot be proper to unite them into one. 



When Dr. Binney published the first description of this shell, in 

 1837, he adopted, without examination, the name zaleta, which he 

 found applied to it in some cabinets, and which he then supposed had 

 been applied by Mr. Say. Finding no description of it, he subse- 

 quently applied the correct name, exoleta, originally suggested, no 

 doubt, by the idea that the species is an old or superannuated form of 

 albolahris. 



Jaw narrow, slightly arcuate, somewhat attenuated towards the 

 ends; anterior surface with 13 ribs; both margins denticulated. 



Lingual membrane (Terr. Moll., V, Plate VIII, Fig. A) with 60-1-60 

 teeth ; 11 perfect laterals, but even the eighth tooth shows a decided 

 modification in form. 



I have already referred to the i)eculiarity of this species in having 

 sometimes and sometimes wanting side cutting points to the outer 

 lateral teeth and a bifurcation to the inner cutting point of the mar- 

 ginals (see Proc. Phila. Acad. Nat. Sci., 1875, 243). I figure in Terr. 

 Moll., V, teeth from a lingual membrane differing in this respect 

 from that figured by me before {I. c, Plate XI, Fig. 7). The cutting 

 points of the central and first lateral teeth have a lateral bulging 

 which represents the side point. This point appears about the elev- 

 enth tooth. Fig. a represents an inner marginal tooth from another 

 membrane, agreeing with mj* former figure in having a simple, not 

 bifid, inner cutting point. I am sure of the identity of each individual 

 examined, having verified it by the peculiar genital bladder and penis 

 sac. 



Genitalia figured by Leidy, Terr. Moll., I, I c. The penis sac is very 



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