﻿MICRO MYA 



33 



Animal with mantle fringed below, maculate on the border, 

 which is greatly thickened at the post-basal part in the female 

 and developed into a flap, with a distinct, toothed ridge inside ; 

 marsnpium occupying the posterior part of the outer branchiae 

 in numerous distinctly marked ovisacs ; inner gill free from 

 abdominal sack in part. 



Type : Undo fab alts Lea. 



Ortmann, (1. c), considers this a subgenus of Burynia. 



Group of Micro mya fabcdis. 



Shell small, with faint, undulate rays, inflated area of female 

 scarcely radiately striated. 



MicROMYA FABALis (Lea). 



Shell small, long ovate or long elliptical, very solid, subin- 

 flated to inflated, inequilateral ; beaks somewhat elevated, sub- 

 compressed, pointed, turned forward a httle over a well-mark- 

 ed kmule, having doubly-looped, subnodulous sculpture; sur- 

 face with irregular growth lines; epidermis ashy-greenish, 

 wavily rayed with dirty brown or brownish-green ; pseudocar- 

 dinals triangular, low, solid, double in the left valve, single, 

 double or treble in the right ; laterals heavy, double in the left 

 valve, often partly double in the right ; muscle scars small, im- 

 pressed ; nacre white or bluish, iridescent behind, thicker in 

 front. Male shell usually long ovate, subinflated or convex. 

 Female shell generally long elliptical, inflated; the marsupial 

 swelling but slightly inflated, not distinctly marked off from 

 the rest of the shell, placed toward the hinder part of the base 

 and occasionally having vestigial radial wrinkles, thinner than 

 the rest of the shell, and excavated within. 



Length (male) 38, height 22, diam. 12 mm. 



Length (male) 30, height 18.5, diam. 14 mm. 



Length (female) 25.5, height 15, diam. 12.5 mm. 



Ohio River drainage ; Rouge River, near Detroit ; New 

 York. 



Type locality, Ohio River. 



