OP CONCHOLOGY. 145 



Dimensions. — Diameter 1 4-10ths inches, length 3 inches 

 breadth 2 inches. 



Habitat. — Black Lake, Michigan. 



Collection Mus. Comp. Zoology, Cambridge, Mass. 



Observations. — Distinguished by its inflated character and 

 dull, dark olive color, in which it somewhat resembles Anod. 

 gibbosa, Say, but it is more equilateral, less inflated, less pon- 

 derous, and the epidermis has not the fine green rays and 

 general green color of that interesting species. The form of 

 the present species in every stage of its growth differs essen- 

 tially from Anod. gibbosa. The color of the epidermis is more 

 like that of Anod. Couperiana, Lea, but in no other particular 

 does it resemble that species. 



3. Anodon inornata, Anthony. — t. 7, f. 1. 



Description. — Shell broadly elliptical, very inequilateral 

 rounded before and sub-biangular behind ; substance of the 

 shell moderately thick; epidermis of a dull ochrey-yellow 

 without rays, deepening into a light brown color on the pos- 

 terior slope ; beaks rather prominent,.with prominent, elevated, 

 and waved wrinkles at tip ; anterior cicatrices distinct and 

 well defined, posterior cicatrices also distinct, but less deep 

 than the anterior ; marks of growth widely separated in the 

 earlier stages of growth, becoming more crowded near the basal 

 edge in old specimens ; nacre silvery and highly iridescent 

 particularly at the posterior end, tinged with salmon color 

 under the beaks. 



Dimensions. — Diam. 1J inches, length 3f inches, breadth 

 2^ inches. 



Habitat. — Michigan, Slawson's Lake. 



Collection of Mus. Comp. Zoology, Cambridge, Mass. 



Observations. — May be compared with Anod. opalinus, Nob. 

 but is less inflated, less angular, is more elongate, and a thicker 

 and heavier shell ; with no other species would it be likely to 

 be confounded. Although the substance of this shell is quite 

 thick, it is, nevertheless, translucent and opalescent; the surface 

 is finely and delicately striate longitudinally and transversely, 

 and, under the microscope, presents an unusually beautiful 

 appearance. 



