ON BOSMINIDiE, HACROTHRICTDvE, ETC. 363 



widening towards the extremity, and of nearly equal breadth 

 throughout, having a small knob-like swelling on the posterior 

 margin close to the base ; and furnished with a few small setse 

 at the distal extremity and on the anterior margin, where they 

 are situated in seven to nine little notches. The peduncle of the 

 posterior antennae of moderate dimensions, the seta of the first 

 joint of the three-branched ramus very long and unusually thick, 

 and furnished on one edge with a few conspicuous spines; the 

 remaining setse of both rami have a spine at the termination of 

 their basal portion. Abdomen edged with spine-like hairs, more 

 conspicuous close to the abdominal setse, thence gradually becom- 

 ing more minute posteriorly, until they are almost entirely absent; 

 but near the claws they again re-appear of much greater length. 

 Eye-spot small, situated close to the extremity of the rostrum. 

 Length, -rg-th of an inch. 



Found in Lochmaben Loch, Dumfriesshire, by Mr. "W. Yarrell ; 

 and in Loughs Cregduff, Bollard, Doon, and Nawheelan, Conne- 

 mara, by G. S. B. Abroad it is known in the neighbourhood of 

 Geneva, in Sweden, and in Germany. 



Genus. DREPANOTHRIX, G. 0. Sars, 



Carapace nearly round, not produced centrally behind, dorsal 

 margin having a distinct sinus at the junction of the thorax and 

 head, and posterior to this furnished with a large thorn-like pro- 

 cess, ventral margin serrulate and ciliate, cilia simple. Anterior 

 antennae large, conspicuous, trunk-like, dependant from the ex- 

 tremity of the rostrum. Posterior antennae having the four- 

 jointed ramus furnished with four, and the three-jointed ramus 

 with five seta? ; the lowermost seta of the latter not geniculated 

 like the others, simple, falciform, spined on one edge. Eye-spot 

 large, quadrangular. Abdomen short, deep, edged with spines, 

 terminal claws very small. Intestinal canal forming a very large 

 loop in the middle of the thorax. An inhabitant chiefly of up- 

 land lakes. 



It will be observed that this genus differs from Macrothrix 

 chiefly in having a large convolution in the intestinal canal, and 



