Notes on CloAocera. 99 



This is, I think, the only case where this distinctively male ap- 

 pendage is found in the female. 



Southampton, Mass., Aug., 1877. Not rare. 



SPECIES 7. 

 Plate II. Fig. 15. 



Pleueoxus Acutirostkis. sp. nov. 



Length, 0.35 mm. Height, 0.23 mm. 



« 



Beak, long, pointed, and bent backward at the tip. Teeth of 

 post-abdomen very fine. Bristles of lower margin of valves stout 

 and plumose. 



In general shape this species closely recalls P. hamatus. It is 

 readily distinguished by the long, pointed rostrum, whose apex 

 nearly meets the valves when in its natural position. The valves 

 are reticulated as in P. insculptus, although not so plainly. There 

 are no teeth on their ventral margin. 



The post-abdomen is broad, compressed, truncated, with numer- 

 ous fine caudal teeth. The terminal claws have only one basal 

 spine. 



In rostrum this species closely approaches Harporhynchus 

 (Sars), as also in the single basal spine of the terminal claws. In 

 general, however, the species is so thoroughly Pleuroxus-like in 

 appearance, that I keep it under that genus for the present. 



Southampton, Mass., July, 1878. Yery rare. 



GENUS 2. 



Chydorus. Leach. 1816. 



Chtdortjs, Leach. Sup. Brit Eacyc, Art. Annulosa.* 

 " Baird, Schodler, Sara, Kurz, P. E. Miiller. 



SPECIES I. 

 Plate II. Fig. 19. 



Chydorus Sph^ricus. O. F. Miiller. 

 One of the oldest and best known species of Cladocera For 

 * Teste P. E. Miiller. 



