882 THE AMERICAN NATURALIST. [VouL. XXXIII. 
the tips of the terminal claws. Mandibular palp much elongated. Palp of 
the first maxilla strongly developed. Second maxilla bears a well-developed 
branchial plate. In the female the palp of the second maxilla is unjointed 
and terminates in three sete ; in the male it forms a hooked prehensile 
organ, and the right and left palp of the male are dissimilar. Caudal rami 
are robust and the dorsal sete are situated about midway of the outer border. 
Eye large. Muscle impressions four. The center of Zenker’s organ sur- 
rounded by seven whorls of chitinous sete. The upper part of the organ 
forms a blind sac, the lower terminates in the funnel-shaped origin of the 
vas deferens. Copulatory organ triangular. Males numerous. 
a. Terminal short setz of the second foot approximately equal. 
6. Terminal short sete of the second foot about two times the 
length of the last joint. Left valve with a dorsal flange ; right 
valve with row of tubercles anteriorly and ventrally 
C. pustulosa Sharpe 
66, Terminal short setæ of the second foot about as long as the 
terminal joint. 
c. Terminal claw of the caudal ramus half the length of the 
ramus. 
d. Shell equivalve. 
e. Covered with a close reticulum of subparallel lines. 
Length 0.54 mm. to 0.64 mm. 
C. exculpta (Fischer) 
ee. Covered with irregularly scattered large puncta. 
Length 0.55 mm. to 0.58 mm. 
C. ophthalmica (Jurine) 
cc. Terminal claw of caudal ramus three fifths the length of the 
ramus or longer. 
d. Shell inequivalve, valves glossy, finely pubescent. 
Length 0.46 mm. to 0.52 mm 
C. ineguivalva Turner 
dd. Shell equivalve, surface smooth, ne hairy. Length 
0.69 mm. C. dentifera Sharpe 
aa. Terminal short setz of the sect foot evidently unequal. 
6. Shell covered with numerous almost confluent puncta. Length 
0.78 mm. > C. mons (Chambers) 
66. Shell not Lisia makai in any way. Dorsal seta of ramus 
three times the width of the ramus from the terminal claws 
C. obesa Sharpe 
5. Cypricercus Sars, 1895. 
“« Natatory sete of both pairs of antennæ well developed; palp and 
masticatory lobe of the first maxillæ narrow. Caudal rami excessively 
developed and elongate, affording a ready means of recognition. Cœcal 
