300 Birge — Notes on Cladocera. 



They are therefore probably somewhat shorter than in Sars ? spec- 

 imens. The basal joint always projects far beyond the head. Their 

 setae are not unusually long. The one borne on the basal joint of 

 the ventral ramus is short, only about one-half the length of the 

 others, but is never absent. 



The post-abdomen is, as Sars says : "eidem in D. longispina sat 

 similis. " It is long and slender with 8-14 anal teeth. The 

 caudal claws are denticulate and have two small anterior teeth. 

 The eye is small and the lenses project far out of the pigment. 

 The other internal organs agree with those of the section 

 Hyalodaphnia. From 2 to 6 young were observed in the brood 

 cavity. The male was not found. 



Length of female, 1-1.5 mm., height, 0.6-0.7 mm. 



The species was found abundantly in material from lakes 

 G-eneva and Delavan, Wisconsin, with D. microcephala. 



Bosmina obtusirostris, Sars, (?) 



Plate XII, Figs. 10, 11. 



A form identical with Sars' species, or very closely allied to 

 it, was collected by Miss H. Merrill near Woods Holl, Mass., in 

 a pool in Fay's Wood. 



Female — Length, 0.6 mm.; height, 0.43 mm. 



The head in front of the eye is very protuberant, but in a 

 peculiar manner. The elevation passes gradually into the dorsal 

 outline but ventrally is bent abruptly in toward the antennules. 

 The ventral line of the protuberance in aged individuals makes 

 nearly a right angle with the anterior margin of the antennule. 

 The rostrum is nearly obsolete. The sense-hair is situated at 

 the point of attachment of the antennules. The antennules 

 are short, slightly curved, and in the adult show only very 

 faint traces of "joints" in alcoholic specimens. The sense- 

 hairs are about one-third of the distance to the tip. In yoang 

 specimens, still sexually immature, the antennules are relatively 

 long, strongly curved and show 12-14 joints beyond the sense- 

 hairs. At this time they are as long, absolutely, as in the 



