STATE GEOLOGIST. 117 



Sp. 3. Chydorus ovalis, Kmz. 

 (Plate F. Fig. 11.) 



Form oval, nearly twice as long as high; beak long; aatennules 

 two-thirds as long as the beak, with two elongated sensory filaments 

 above the others; pigment fleck nearly as large as the eye; antennae 

 small; shell margins heavily fringed anteriorly; post-abdomen of 

 moderate size, rounded at the end, with about 8 teeth near the end; 

 shell smooth. Length 0.4 mm. 



This species is rather near C. sphasricus, differing in having the 

 shell smooth, antennse shorter, and beak longer. This species is 

 not yet known in America. 



Sp. 4. Cliydorus cfelatus, S hoedler. 



(Plate F. Fig. 12.) 

 Chydorus adunctus, Schoedlek. 



This small species is about 0.4 mm. long, and resembles the young 

 of C. globosus in form, from which as well as from all known spe- 

 cies it is distinguished by the marJdngs of the shell, which consist 

 of series of rounded elevations (or depressions?) arranged parallel 

 to the lower margins of the shell and head. The description is very 

 incomplete, and the only other author who appears to have seen 

 the animal is Kurz, who adds that the sensory filaments of the sin- 

 tennse are unequal in hight, and that the so called elevations are 

 really depressions. A form with a few depressions about the edge 

 and characters of this specias was once seen in the vicinity of Min- 

 neapolis. 



Sp. 5. Cliydorus nitidus, Scboedler. 



(Plate F. Figs. 5, 6.) 



Shell smooth and regularly punctate; the head resembles C. sphee- 

 ricus, but the pigment fleck is much smaller thad the eye, to which 

 it is much nearer than to the end of the beak; the post-abdomen is 

 broader near the end, and bears a row of 10 — 12 teeth on either side. 



(?) Sp. 6. Cliydorus latus, Sars. 



Very possibly a variety of C. globosus, from which it differs in 

 the shorter beak and greater size. Length 0.66 mm. 



