204 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 



Kurz for his B. vitrea gives a leDgth of 0.85 mm. plus 0.25 ram., the 

 length of the spine. Judging from his figure, the head would not 

 measure over 0.35 mm. 



Forbes says of his D. retrocurva that the head is two thirds as long 

 as the body. 



Our specimens measured as follows: 



No. 1. 1.6 mm.; head somewhat more than half the body and 

 almost exactly like D. vitrea in form. 



No. 2. Head 0.6 mm., body 0.9 mm., spine 0.5 mm.; about nine 

 anal spines. Head in this case moderately curved upward. 



No. 3. Head 0.95 mm., body 0.95 or less, spine 0.5 mm.; or the 

 head as long as, or, indeed, considerably longer than, the body and 

 directed upward. 



The males have the crest much lower, the spine longer, and the 

 form of antennules figured by P. E. Mueller. In the older females the 

 beak is elevated above the antennules, as remarked by Forbes, but in 

 smaller individuals there is very little difference between our speci- 

 mens and Mueller's figures. 



The claws of the post-abdomen have, besides the row of fine teeth 

 mentioned by Mueller, a cluster of sharp teeth just at the base. 



Found, together with typical D. galeaia and the rounded form, in 

 a small deep lake or expansion of a creek not far from Medicine lake, 

 Hennepin county, Minnesota. 



"We have since found this species at a depth of 80 feet in Lake Min- 

 netonka, and here also in association with 7>. hyalina. The range of 

 variation is exceedingly great as indicated by the figures of Plate 



Lin. 



Having given as full a catalogue of the well known and accessible 

 species as our circumstances now permit, it remains to notice the ex- 

 istence of others which are either imperfectly described or the descrip- 

 tions are out of reach. 



Daphuia siniilis Claus. 

 Plate XXXV, Fig. 5; LI, Fig. 7. 



The description of this species, which was bred in confinement from 

 eggs brought in mud from Jerusalem, I am, unfortunately, unable to 

 quote. Judging, however, from the figures which alone I now have 

 access to, it belongs in the group of B. longispina, though in many 

 particulars it resembles B. schccjfferi. The form is elongate, the spine 

 short and springing from the upper margin. The anteuuule of the 

 female is very large and flagellate, while that of the male is like that 

 of B. schcefferL The flagellum and hook of the first foot of male are 

 rather small. 



