of British Entomostraca. 411 



inferior or large antennse, the rami of Straus. In these three 

 genera, which have been all adopted by Milne Edwards, the su- 

 perior antennae (antennules of M. Edwards) in most of the species 

 are exceedingly small compared with the inferior, so much so 

 indeed, as almost to have escaped the notice of Miiller altogether. 

 They are also situated beneath the beak. In the two species 

 however which I have mentioned above, they are very much 

 larger than in the others, and instead of springing from the 

 head under the beak, hang pendulous from or are articulated 

 to the beak itself. In the Daphnia rosea [Macrothrix roseus) 

 they are flat, one-jointed and distinctly pendulous from the beak, 

 occupying such a position that they cannot be mistaken or over- 

 looked. 



In the Daphnia cornuta however, from the extremely minute 

 size of the little animal, they have been hitherto constantly mis- 

 understood by observers, and though much too large and promi- 

 nent to be overlooked, they have been described as a totally dif- 

 ferent organ. Having last autumn met with this curious little 

 creature in great abundance in the water from the Hampstead 

 ponds, I have been enabled to place it under a microscope of high 

 power, and have thus succeeded in ascertaining the real struc- 

 ture and position of these organs. In the notices of this species 

 by Miiller, Jurine and M. Edwards, the antennules are not men- 

 tioned at all, but the animal is described as possessing a long 

 beak * ; and certainly at first sight and with a low magnifying 

 power these organs appear as being merely a prolongation of the 

 anterior part of the head, similar to what we see in many of the 

 LynceidcE. This is not so however, and upon a careful investi- 

 gation I have found this apparent beak to consist of two long, 

 curved, cylindrical bodies, consisting each of about twenty small 

 articulations, and united to the beak or anterior part of the head 

 by a distinct joint. In structure these organs resemble very much 

 the antennae of the Cyclopida, but like the antennules of the other 

 Daphnice possess very little motion. Miiller considered this ani- 

 mal to be a LijncevSj and led away by the above-mentioned re- 

 semblance to the beak of many of that genus, he has described 

 it under the name of L. longirostris f. Jurine has described it 

 under the division of Monoculi belonging to the group of the 

 DaphnidcB, under the name of Monoc. cornutus, and has been fol- 

 lowed by Desmarest and M. Edwards. In the ' Ann. Mag. Nat. 

 Hist.^ I have also described it under the name of Daph. cornuta^ 

 not having then distinctly seen the structure of the antennules. 

 These are so peculiar however in their structure and position, and 

 so distinct from those of the other Daphniday that in the ^ Trans. 



* '' Le bee est long et gros." — Edwards. 

 t Entomostraca, p. 76. t. 10. f. 7, 8. 



2F2 



