118 TWELFTH ANNUAL RErORT. 



Sp, 7. Chydoriis piger, Sars. 



Sub-rotund, prominent above, sinuate behind; lower and poster- 

 ior margins rounded, lower margin ciliated. Head movably united 

 to the body; beak long, separated by an indentation from the head 

 shield. The shell is broad, as seen from above. Shell punctate 

 anteriorly and marked below by indistinct oblique strife. Anten- 

 nules with seven sette and two small thorns on the end of each 

 ramus. Post-abdomen truncate; the terminal claws with a minute 

 tooth at the base; posterior margin siuuated, rounded below and 

 there densely armed with minute teeth. Abdominal setas long and 

 flexible. Pigment fleck of medium size, much nearer to the eye 

 than to the beak. Length about 0.33 mm. 



(?) Chydorus latifrons, Dana. (U. S. Exploring Expedition, Rep. on Crust., 



vol. II, p. 1274.) 



Very tumid; in side view rotund, head not separate, very short- 

 beaked; beak slender and close to the body, acute; in upper view 

 animal very broad, truncate anteriorly, the front thereby nearly 

 as broad as the body; behind low, triangular and obtuse. Feejee 

 islands. 



( ?) Chydoiais albicans, Gay, 



from Chili, is imperfectly described; but it is interesting to note the 

 occurrence of this genus there. 



X. — Genus Anchistropus, Sars, (?) 



Very similar in form to Chydorus; valves gaping below anteri- 

 orly; antennules small; process of labrum rounded. Post-abdomen 

 attenuated toward the end, densely covered with fine teeth; terminal 

 claws denticulate. First foot with a powerful claw, protruding 

 beyond the shell. Eye very large. Shell indistinctly reticulate. 

 Sars says of his Anchistropus emarginatus that on cursory inspec- 

 tion it would be taken for the young of Chydorus globosus. He 

 found but few specimens, about 0.35 mm. long. The suggestion is 

 still possible that the young males of some Chyd'^rus are here mis- 

 taken for a new genus. The males of Chydorus globosus were not 

 known till 1878, and their early form is still unknown. The young 

 females have a tolerably strong claw, though it is not much curved. 

 I have once found a peculiar lynceid measuring 0.46 mm., with 



