The Crustacea of Cambridgeshire 



round creature with comparatively small second antennae and 

 a compound eye, which is very inconspicuous when compared 

 with the largo structures ill the Daphnidae. /w//y/rr/vv/s 

 Ittinelldtus is also common, and from the characteristic 

 like nature of the abdomen, is easily distinguishable. It 

 has been taken in the river Cam, as well as in various streams 

 and ditches. The fen ditches near Reach have proved a 

 happy hunting-ground for Cladocera. In addition to most 

 of the forms already mentioned, we find species of A!<>n, 

 Pleuroxus, and Ceriodaphnia, with an abundance of the 

 highly characteristic Polyphemus pediculus. This latter, as 

 its name denotes, is possessed of a relatively enormous com- 

 pound eye, and when swimming in the water, this large black 

 spot, together with the brownish U-shaped intestine, are alone 

 conspicuous, owing to the transparency of the remaining 

 parts. 



Finally, an interesting form is Macrothrix hirsuticornis, 

 taken in the village ponds at Barton. The animal in question 

 would seem to come nearest to the specific definition of 

 Jtirsuticornis, but is unaccountably large. Even if merely 

 M. hirsuticornis, the capture is interesting, as the specie 

 only recorded from four other localities in the British Isles. 



OSTRACODA. A number of these small crustaceans, with 

 their bivalve shells and almost mussel-like appearance, are 

 fresh-water forms, though again a great variety are strictly 

 confined to the sea. Unfortunately the records in this case 

 are more incomplete than for the Cladocera, but there seems 

 little reason to doubt that the district would furnish a con- 

 siderable collection to anyone expending time and trouble on 

 the matter. All the forms at present recorded appear to 

 belong to the single genus Cypr'is, if we except a note by 

 Jenyns which seems to refer to the form now known as \otv- 

 dromus monachus. Cyjirix J'iw<ita of a large size has heen 

 taken in great numbers on Sheep's Green, nnd we may al>> 

 mention C. vireits and C. pubera, the latter from Bottisliam 

 Fen. 



