SCAMMON : THE UNI0NIDJ3 OF KANSAS, PART I. 361 



impressed, striated ; retractor 'pedis muscle scar oval, very 

 deeply pitted, striated ; dorsal muscle scars situated on the 

 posterior face of the cardinal teeth and the under side of the 

 connecting bridge, deep, large ; pallial line impressed ; cav- 

 ity of the beaks deep ; nacre silvery white, more or less iri- 

 descent." (Baker, 2.) 



Q. trigona occurs throughout the Mississippi drainage, north 

 into the St. Lawrence and south into Alabama. It has been 

 reported from all the larger streams of southern Kansas and 

 from Bull creek at Paola (Call), in the Marais des Cygnes 

 drainage. 



Trigona is close to Q. rvhiginosa but is a more inflated and 

 heavier shell, with more massive dentation. 



Quadrula coccinea Conrad. Plate LXXXIV, fig. 1. 



Unio coccineus Conrad, Mon. Fresh-water Shells, in, 1836, p. 29, pi. xill, 



Shell of moderate size and solidity, suborbiculate in out- 

 line, slightly compressed. Anterior margin flatly or fully 

 rounded, ventral margin gently bowed ; posterior margin bi- 

 angulate, produced below, straight or slightly curved, quite 

 oblique, set at an angle ; dorsal margin straight or slightly 

 curved, oblique, joining the posterior margin at an angle of 

 from 130 to 150 degrees Umboidal ratio extremely variable. 

 Umbones quite high and moderately full, marked with nu- 

 merous fine concentric ridges and three coarse broken ones. 

 Lateral and anterior slopes flatly rounded ; posterior slope 

 slightly incurved ; posterior umboidal ridge not prominent, 

 rounded. Epidermis smooth, shining, over umbones horn 

 color to dark reddish brown, with the umboidal region covered 

 with bright green rays of variable width. Lines of growth 

 coarse, heavy, and often imbricated. Ligament thick, of 

 moderate length. Luuule cordate. 



Interior : Pseudocardinals of medium size and variable 

 height, double in the left and single in the right valve, the 

 right pseudocardinal surrounded by a trench. Interdentum 

 long, width variable, cut away in the right valve. Laterals 

 long, oblique, straight, or slightly curved, heavy, striate, 

 sometimes double in each valve. Anterior adductor scars 



