438 Illinois State Laboratory of Natural History. 



daily noticeable at the highest dorsal part just in front 

 of the eye-spot. Its surface is covered with numerous 

 papillar elevations and scattered hairs. It is also finely 

 pitted over its entire surface (Fig. 2), these pits show- 

 ing to better advantage should the specimen partially 

 project from its medium and be examined with reflected 

 light. 



Seen from the side, the dorsal margin is arched, 

 highest at its posterior third. Ventral margin very 

 slightly sinuate. 



Seen from above, the shell is broadly ovate, nar- 

 rowed in front, the right valve being somewhat over- 

 lapped by the left. The anterior and posterior margins 

 of the right valve are armed with a row of small tuber- 

 cles (Fig. 2), which give it a serrated appearance. 



Setae, of the mandibular palps plumose. Natatory setae 

 strongly plumose, extending as far beyond the terminal 

 claws as the length of these claws. The spines on the 

 first process of the first pair of maxillae are strongly 

 toothed. 



Second foot moderately stout, the terminal claw much 

 bent and but little longer than the terminal segment. 



Caudal rami (Fig. 1) rather stout for members of this 

 genus, about thirteen times as long as wide, broadened 

 at the base. Terminal claw slender, curved, finely toothed 

 near its tip, and four sevenths as long as the ramus ; sub- 

 terminal claw not quite three fifths as long as the term- 

 inal one. Terminal seta four fifths as long as subterminal 

 claw; dorsal seta slightly longer than the terminal one 

 and twice the width of the ramus from the subterminal 

 claw. 



Pt. Pinellas, Fla., May 12, 1885 (Coll. 111. State Lab» 

 Nat. Hist.); Cincinnati, 0., 1893 (Turner). 



lY. CYPRIS O. F. MULLER. 



1792. Cyvris, O F. M. (49, p. 48). 

 1820. Monoculus, Jurine (36, p. 170). 



1868. Cypri^, Brady (6. p. 360). 



