SCAMMON : THE UNIONID/E OF KANSAS, PART I. 357 



analogous to the alse of the true winged Unios. Lateral slope 

 ornamented with two radial rows of small, erect pustules, 

 arranged linearly, and from three to five in number, some- 

 times with a group of irregularly placed pustules at the mar- 

 ginal end of the rows ; posterior slope bearing a few obscure 

 pustules arranged in five or six transverse rows. Epidermis 

 light to dark horn color, with sometimes a light cast of 

 green ; young specimens show a green triangular patch over 

 the umbones. Lines of growth far removed, considerably 

 darker than the epidermis of the body of the shell. Lunule 

 small and cordate in outline. Ligament stout and thick. 



Interior : Pseudocardinals large for the size of the shell, 

 erect, ragged, double in the left and single in the right valve ; 

 the left anterior pseudocardinal generally the larger, the right 

 pseudocardinal arising from a pit. Interdentum broad but 

 very short. Laterals at right angles to the free edge of the 

 interdentum, straight or slightly curved, oblique, fairly long. 

 Anterior adductor cicatrix deeply excavate, semicircular in 

 outline, placed in front of the pseudocardinals; posterior 

 scars small, lightly impressed, confluent. Pallial line im- 

 pressed its anterior two-thirds. Dorsal cicatrices on the base 

 of the pseudocardinals. Cavity of the shell small, of the 

 beaks rather large. Nacre milk-white, very slightly iridescent 

 posteriorly. 



Quadrula puskdata occurs in the lower half of the Mississippi 

 drainage, in the Ohio river system, and in southern Michigan. 

 In Kansas it is found only in the Verdigris river and the 

 Neosho, in the southern drainage. 



Q. pustulata is generally confused with its near ally, Q. 

 pustulosa. It is, however, quite a distinct species. In the 

 form under discussion the dorso-posterior angle is produced 

 in a manner rarely found in pustulosa, and the arrangement 

 of the tubercles is entirely different. The tubercles of Q. 

 pustulosa are scattered irregularly over the disk ; those of Q. 

 pustulata are arranged in two radial rows which extend from 

 the umbones to the ventral margin ; they are set far apart, at 



6-BuU., Vol. Ill, No, 9. 



