SCAMMON : THE UNIONID.E OF KANSAS, PART I. 317 



other, and a well-developed posterior ridge, the space be- 

 tween the ridge and the knobs somewhat excavated ; posterior 

 slope and sometimes the whole shell more or less corrugately 

 sculptured; beaks prominent, incurved, and pointed slightly 

 forward towards a tolerably well-developed lunule ; beak 

 sculpture strong, consisting of four or five heavy, parallel 

 ridges, which fall low in front but are curved up behind ; 

 epidermis smooth, generally shining, painted with numerous 

 delicate, wavy, darker, broken rays ; pseudocardinals strong, 

 direct, and ragged ; laterals short, nearly straight ; anterior 

 muscle scars small, sides of the pit smooth, bottom ragged ; 

 front part of shell very solid, suddenly becoming rather thin 

 just behind the knobs; male and female shells essentially 

 alike. 



'Animal with small branchipe, rounded below, inner the 

 larger, free from the abdominal sac in part ; marsupium of a 

 few distinctly marked ovisacs (4 to 7), occupying a position 

 just behind the center of the outer gills, projecting far below 

 the rest of the branchise, their bases rounded ; mantle cut 

 away at the thinner portion of the shell ; anal opening smooth 

 or having only minute crenulations." (Simpson.) 



Obliquaria reflexa Rafinesque. Plate LXXI, fig. 1. 



Obliquaria reflexa Rafinesque, Ann. Gen. Sci. Phys., 1820, p. 306. 

 Unio cornutus Barnes, Amer. Jour. Sci. and Arts, VI, 1823, p. 122, pi. 

 iv, figs. 5, 5a, 56, 5c. 



Shell rather small, inflated, thick anteriorly, of only mod- 

 erate thickness posteriorly, outline variable, wide or narrow, 

 ovate, pointed posteriorly. Anterior margin and anterior half 

 of ventral margin forming a semicircular curve, posterior 

 position of ventral margin curved or straight, sometimes 

 slightly emarginate ; posterior margin short, commonly join- 

 ing the dorsal margin at an angle of from 130 to 145 degrees 

 but sometimes forming a common curve with it. Umboidal 

 ratio, one-fourth to one-third. Umbones large and full, in- 

 curved, marked with several heavy ridges. Anterior umboi- 

 dal slope fully rounded ; lateral slope ornamented with a series 

 (generally four) of large, prominent knobs, which are located 

 in a slightly curved line and are about twice their diameter 

 apart, the area between them slightly excavated ; knobs alter- 



