SCAMMON : THE UNIONID^ OF KANSAS, PART I. 329 



cast, obscurely marked with numerous fine greenish rays, 

 which extend over the anterior and lateral slopes ; the um- 

 bones often of an olive-gray color. Lines of growth promi- 

 nent, raised, but smooth anteriorly, imbricated posteriorly. 

 Ligament long, fairly stout, of a light brown color. 



Interior : Hinge line gently bowed. Muscle scars large and 

 faint; the anterior scars of almost equal size, and distinct; 

 the posterior scars confluent. Pallial line hardly visible, 

 wavy. Cavity of shell large, of umbones very large. Nacre 

 silvery or pinkish, moderately iridescent. 



Length. Height. Breadth. Um. ra. 



119 82 54 42 (Coll. W. C.) 



A. opaca is a Southern species. Its range is from Louisi- 

 ana and Mississippi north to Kansas. I know of only one 

 locality for this form in Kansas : Quimbly creek, in Clay 

 county, a small tributary of the Kansas drainage. Doubtless 

 it also occurs in the southern series of the state. 



This form can hardly be confused with any other Anodon. 

 It resembles A. grandis in coloring and slightly in outline, 

 but the ratio of the height to the length in grandis is as 1 to 

 2, while in the form under discussion it is as 2 to 3. The 

 high and extremely full beaks are very characteristic. 



Genus ANODONTOIDES Simpson. 



" Shell elliptical, inflated, thin, with a faint posterior ridge, 

 sometimes constricted at the center of the base ; beaks rather 

 fullj with a few coarse, subparallel, concentric ridges, which 

 are curved up rather suddenly behind, and back of these are 

 some fine radiating ridges ; epidermis smooth, shining, often 

 rayed ; hinge line slightly incurved in front of the beaks, 

 edentulous or bearing the merest rudiments of teeth ; muscle 

 scars shallow, irregular; nacre bluish white. 



"Animal with the marsupium occupying the outer and 

 sometimes the four leaves of the branchiae ; ovules more 

 numerous in the outer, the whole pad-like ; gills large, inner 

 semicircular, free from the abdominal sac or united to it ; 

 branchial opening large, with many small papillae ; anal 

 opening with well-developed papillae." (Simpson.) 



