•t:52 Illinois State Laboratory of Natural History. 



conical, the penultimate three fifths as wide as long, the 

 antepenultimate two thirds as long as the penultimate, 

 and all three combined scarcely as long as the one pre- 

 ceding them. 



Feet of the second pair (Fig. 7) six-segmented, the 

 fourth segment being divided ; terminal segment as long 

 as wide, the shorter backwardlj directed seta two and 

 a half times as long as the segment, the longer one 

 three and a half times as long as the shorter one. 



Caudal rami (Fig. 11) well developed, long, straight. 

 Terminal claw half as long as the ramus, evenly and 

 gently curved, toothed at middle; subterminal claw 

 similar but a tenth shorter. Dorsal seta three fifths the 

 length of the subterminal claw and at two thirds its 

 length from the claw; terminal seta a third the length 

 of the dorsal one. The base of the ramus is broad. A 

 short distance below the base is a small sinus or inden- 

 tation (Fig. 11) which seems peculiar to the species. 



Described from a few specimens in the collections of 

 the Illinois State Laboratory of Natural History, ob- 

 tained from ponds at Clifton, 111., Feb. 16, 1882. 



Candona simpsoni n. sp. (PI. XLVL, Fig. 1-6.) 



A small elongate species .73 mm. long, ,30 ram. high, 

 and .29 mm. wide. 



Left valve slightly overlapping the right (Fig. 4) ; sur- 

 face of shell covered with a few conical papillar eleva- 

 tions. Color grayish to yellowish white or cinereous. 



Seen laterally (Fig. 3), the shell is elongate-elliptical, 

 two and a half times as long as high, evenly rounded 

 anteriorly, somewhat more pointed posteriorly, where 

 the dorsal margin slopes more rapidly than the ventral 

 margin. The dorsal edge is very slightly sloping, nearly 

 straight, the ventral edge being slightly sinuate in the 

 middle. 



Seen dorsally, its greatest thickness equals its great- 

 est height; outline subelliptical, the anterior part some- 

 what more acutely pointed than the posterior, which 



