402 REV. A. M. NORMAN AND MR. Q. S. BRADY 



form of a broad flattened blade, with a very closely serrated mar- 

 gin, serrations smallest near the abdominal setae and gradually 

 increasing in size towards the claws, distal extremity of abdomen 

 abruptly truncate on the supero-posteal portion, but produced 

 inferiorly into a process of considerable size, which is margined 

 on either side with a row of articulated spines, and supports the 

 terminal claws; claws strong, acute, but little curved, ciliated 

 on the edge, and having two spines attached to their base. 

 Length, -roth of an inch. 



Perhaps the commonest member of the family : occurring in 

 ditches, small ponds, canals, slow-running rivers, and lakes. It 

 inhabits the whole of northern Europe, but is not among the 

 Entomostraca described by Jurine from the neighbourhood of 

 Geneva. 



Genus. MONOSPILUS, G. 0. Sars. 



Carapace composed of a series of valves laid one over another. 

 Head depressed ; rostrum produced, acute. Compound eye wholly 

 absent, eye-spot present; one branch of posterior antenna? fur- 

 nished with four seta? and a spine, the other with three setas and 

 two spines. Abdomen short and unusually broad, with numerous 

 spines varying greatly in size, irregularly disposed on the edge 

 and sides. Inhabiting lakes. 



This genus was established by Gr. 0. Sars in 1861 for the recep- 

 tion of an Entomostracan which he had met with in Norway, 

 and named Ifonospihis disjpar ; the species however is evidently 

 the same as that described, many years previously by Eischer, in 

 the "Bull, cle Soc. Imp. cles Nat. de Moscow," under the name 

 Lynceus tenuirostris. 



The most remarkable features in Ilonospilus are the peculiar 

 structure of the carapace and the total absence of the usual com- 

 pound eye of the Cladocera. The only organ of vision (if organ 

 of vision it be) is the simple eye-spot, which occupies its usual 

 position. Sars, remarking upon this, observes — "Macula nigra 

 unica minima prope basin antennarum secundi paris, ruaculse in- 

 fraoculari in ceteris Lynceidis simillima, in capite conspicitur ; 

 quae, quum oculus verus compositus in omnibus ceteris Crustaceis 



