11 



tains the crested forms of the DaphninaB, and thus recalls the 

 genera Acroperus and Camptocercus, among the Lynceidse. Like 

 those genera, too, the members of this group are transparent, and 

 their post-abdomen is narrow and elongated, although by no 

 means to so great an extent as in the Lynceid genera. 



No subsequent writer has agreed with Schodler in distinguish- 

 ing Hyalodaphnia from Daphnia. And with good reason, since 

 the sole characteristic of the genus is the absence of the macula 

 nigra ; and as this structure is small or rudimentary in all the spe- 

 cies of Daphnia, its absence does not form a generic difference. 



Daphnia is not a genus typical of the sub-family Daphninas, 

 but is rather an extreme form. Moina is the least specialized. 



SPECIES 1. 

 Plate I. Fig. 11. 



Daphnia Pulex. De Geer, var. denticulata. var. nov. 



For the long synonymy of this oldest and best known of Clado- 

 cera, see Baird, British Entomostraca, and P. E. Miiller, Dan- 

 mark's Cladocera, p. 110. 



In size, shape and markings, this animal agrees with D. pulex. 

 There are, however, some differences. The lower margin of the 

 head is not so convex as in D. pulex. The abdominal processes 

 are very slightly hairy, or not at all so, instead of being covered 

 with hairs. The terminal claws, like those of D. pulex, are 

 armed with teeth at their base, but have besides a row of very 

 fine teeth extending along the whole length of the claw. The 

 number of abdominal teeth is greater than has been noted in 

 D. pulex, being 18-20 instead of 15, the highest number noted in 

 D. pulex (P. E. Miiller, T. I, fig. 4). On these grounds I make 

 it a distinct variety, named from the teeth on the terminal claw. 



Cambridge, Mass.; Madison, Wis. 



I have seen a blind specimen of this species. The eye-capsule 

 was ruptured, and the lenses and pigment scattered in the cavity 

 of the head. The optic muscles and ganglion were in great 

 part absorbed. It was a large and healthy animal and lived 

 nearly a week in captivity, when it was eaten by a neuropterous 



