SCAMMON : THE UNIONID/E OF KANSAS, PART I. 321 



with P. clintonense (given below) and with Unio gibbosus. The 

 beak sculpture of the form under discussion consists of nu- 

 merous fine ridges, while the umbone ridges of U. gibbosus are 

 few and extremely coarse. However, owing to the peculiarly 

 soft character of the shell substance, the beaks of phaseolus 

 are almost always much worn. The epidermis of pliaseolus 

 is lighter and more cloth-like in texture than that of gibbosus, 

 and the adult gibbosus is eradiate. The lateral teeth of gibbosus 

 are longer than those of phaseolus. 



Ptychobranchus clintonense Simpson. Not figured. 



Ptychobranchus clintonensis Simpson, Proc. Acad. Nat. Sci. Phila., 

 ' 1900, pt. 1, p. 79, pi. 5, fig. 3. 



"Shell elongate, elliptical, sometimes slightly obovate, 

 feebly biangulate behind, quite solid, beak sculpture not 

 seen ; epidermis somewhat cloth-like, dirty olive, the hinder 

 two-thirds of the shell ornamented with delicate, wavy, capil- 

 lary rays ; pseudocardinals low, laterals very heavy, remote ; 

 muscle scars large and well defined ; nacre lurid, with green- 

 ish-brown blotches. Length, 73; height, 40; breadth, 22." 

 (Simpson.) 



This species is described by Simpson from the Little Red 

 river near Clinton, Ark. I have a number of specimens from 

 Spring river at Baxter Springs which will probably fall un- 

 der this species, but until there is more material in better 

 condition at hand for identification I list this species for the 

 state as doubtful. It is quite close to the preceding one. 



DIAGEN.&:. 



"Male and female shells alike; embryos contained in the 

 outer gills in short ovisacs, which run crosswise of the bran- 

 chise, and are discharged entire into the water." (Simpson.) 



Genus STROPHITUS Rafinesque, 1820. 



"Shell elliptical to rhomboid, inflated, subsolid, pointed 

 or biangulate behind, with a low posterior ridge which is 

 sometimes double; beaks full, sculpture consisting of a few 

 strong concentric ridges which curve sharply upward behind ; 

 epidermis rayed or ray less, shining; hinge line incurved in 

 front of the beaks ; teeth rudimentary, a vestigeal, compressed 



