13 



hepatic coeca are quite small, often rudimentary, being greatly 

 reduced in size, their cavity obliterated and their tissue degen- 

 erated. Specimens of every age, except very young, may show 

 this peculiarity. The " haft-organ '' is wanting in adults, though 

 found in embryos. 



The male resembles in shape the new born female. The an- 

 teunules are movable, short and stout, with a flagellum, and a 

 cluster of sense-hairs, not on the end of the antennule, but a lit- 

 tle proximad. The " haft-organ " is present. 



So far as I know, this is the only crested species with a macula 

 nigra in which the terminal claws are smooth. The name is 

 given on account of this peculiarity. 



I found this very beautiful species only in a small, muddy pool 

 near Mt. Auburn Station, Water town, Mass., 1875. It was pres- 

 ent in great numbers, and with a copepod formed the entire crus- 

 tacean life of the pool. 



Sub-family 2. Lyncodaphninae. 



GENUS 1. 

 Lathonura. Liljeborg, 1853. 



Lathonura, Liljeborg. 1. c, p. 55. 



" Schodler, Sars, P. E. Muller. 



Pasithea, Koch, Leydig, Lieven. 

 Daphnia, e. p. O. F. Muller. 



SPECIES 1. 



Lathonura Bectirostris. O. F. Muller. 



Daphnia rectirostris, O. F. Muller. Entomostraca, p. 92, Tab. XII, fig. 



1-3. 

 Pasithea " Koch. 1. c, H. 35, Tab. XXIV. 



Lieven. 1. c, p. 42, Tab. XI, fig. 1-3. 

 Lathonura " Liljeborg. 1. c, p. 57, Tab. IV, fig. 8-11; V, 2; 



XXIII, 12-13. 

 P. E. Muller. 1. c, p. 139. 



The male of this species I have once seen. It is smaller than 

 the female, being about 0.5 mm. in length, while the female may 





