74 TWELFTH ANNUAL REPORT. 



followed by a series of fringing bristles. The length, according to 

 Mueller, is 1.5 mm. This is a rare form in Europe. 



VI. Genus Ofryoxus, Sars. 



The single species constituting this genus seems to have been 

 seen by no writer save Sars. At the time ray previous paper on 

 Cladocera was published, Sars' description seemed not to apply ta 

 the form called Lyncodaphnia. Since then several stages in the 

 growth of Lyncodaphnia have been encountered, which so far agree 

 with what is said of Ofryoxus gracilis that it is doubted if the two 

 forms are not identical. 



VII. Genus Lyncodaphnia, Herrick. 



(Plate B. Figs. 12, 15; Plate Bi, Fij^:^. 1, 3.) 



Body elongated, somewhat rectangular as seen from the side, 

 greatest width and hight of shell a little posterior to the heart; 

 head separated by a depression from the body, truncate below; 

 antenna? and antennules much as in Macrothrix; -i-jointed ramus 

 of antennae with no lateral seta?; eye small, pigment fleck present; 

 intestine twice convoluted, expanded posteriorly, with anterior but 

 no posterior cgeca, opening near the *' heel " of the post-abdomen: 

 post-abdomen large, triangular; terminal claws long, rather straight,, 

 with two accessory spines at the base. 



The species upon which this genus was founded ^ occurs in 

 August and September in the larger lakes of Minnesota. 



Lyncodaphnia is, as was suggested, a curious transition form 

 linking the Daphnidae with the Lynceidae. 



A farther study of the genus shows that, in some respects, it is 

 more closely allied to both groups than before suspected. The habit 

 and appearance in the water reminds us of Simocephalu?, a re- 

 semblance which an occasional spot of pink or blue color hightens. 



L. macrothroides not only has the disc-like last foot colored but 

 the swimming antennae are banded with purple as in Simocepha- 

 lus rostratus, Her., and S. americanus, Birge. The intestine has 

 anterior caeca, which is not the case in lynceids nor, indeed, in 

 other Lyncodaphnidae. 



The four-jointed ramus of the antennae approaches Lynceidae in 

 the absence of a lateral seta, but the other ramus is as in Macro- 

 thrix. The convolution of the intestine, the form of the post- 

 abdomen and the situation of the anus, are all of a strictly lynceid 



1 Notes on Minnesota Cladocera, p. 247. 



