ON BOSMINIDiE, MACKOTHEJCID^, ETC. 357 



inner edge. Intestine simple, vent terminal, immediately below 

 the claws. 



In the male the first feet are furnished with a hook as in the 

 Lyncei; the abdomen becomes gradually narrower towards the 

 termination instead of being abruptly truncate at the end ; and 

 the anterior antennae are movable, being articulated at the point 

 of junction with the head. 



1. Bosmina longirostkis, (Mutter.) PL XXII, fig. 4. 



1848. Eunica longirostris, Lievin. Die Bran chiopoden der Dan - 

 ziger Gegend, p. 37. PL VII, figs. 8-11. 



1860. Bosmina longirostris, Leydig. Naturges. der Daphniden, 



p. 205. PL VIII, fig. 60. 



1861. Bosmina longirostris, Gr. 0. Sars. Om de i Omegnen af 



Christi. forekom. Cladocerer, p. 11. 



Head erect, not tumid above, rostrum moderately long ; ante- 

 rior antennae one-third to one-half as long as the entire animal, 

 curved, sometimes reflexed at the tips ; bending outwards on 

 each side. Postero-ventral angles of carapace produced down- 

 wards into spine-like processes of moderate length, not exceeding 

 the length of, though much broader than, the abdominal claws. 

 Supero-posteal angle of abdomen well rounded ; margins entire, 

 not crenated or spinous, terminal claws very slightly ciliated. 

 Surface of shell punctated, and reticulate ; reticulation generally 

 faint, often indistinguishable in mounted specimens. Length, 

 - 8 Vth of an inch. 



Prequent in lakes and other clear water. 



"We have felt great doubts whether all the Bosminae which we 

 have met with (except the very distinct B. Coregoni), should be 

 assigned to one, or whether they constitute two or more species. 

 Scarcely two mountings are exactly alike. Specimens from dif- 

 ferent localities vary greatly in size — in proportions of length and 

 breadth — in the amount of sculpture of the carapace — in the 

 exact length of the anterior antennae, &c, &c. ; yet we are un- 

 able at present to find good specific characters. The two more 

 marked forms we have in this paper distinguished by Leydig' s 



