D1NEMOURA. 283 



been done. Dr. Johnston has described two species be- 

 longing to this restricted genus, but under the name of 

 Paiidarus, both of which species were taken at Berwick- 

 upon-Tweed. 



Anatomy. The body of the animals belonging to this 

 genus is of an oblong shape, resembling considerably that 

 of the Caligidae, and divisible, as in them, into head, 

 thorax, and abdomen. 



The cephalo- thorax, including the head and the first 

 ring of the thorax, is in form of a shield or buckler, and 

 somewhat of the same form and sculpture as in the 

 Caligida?, being divided into several distinct portions, as 

 in them, by deep furrows. The thorax is longer and 

 narrower than the carapace. 



The articulations are very indistinct ; but M. Edwards 

 enumerates five. The first is confounded with the head, 

 and the second and third are small, and so united to- 

 gether as to appear only one. It is of a quadrilateral 

 form, and occupies the space left by the deep notch in the 

 posterior part of the carapace. The fourth segment is 

 about the size of the two preceding, but has attached to 

 it two large moveable plates, which cover the whole arti- 

 culation, and extend, like the elytra of insects, over part 

 of the succeeding joint also. The fifth or last ring is the 

 largest of all, and extends beyond the abdomen, nearly 

 concealing it altogether. It terminates posteriorly in two 

 rounded lobes, which have a deep notch between them, in 

 which is seen the abdomen. This part of the body is 

 small, of a square shape, and has appended to its ex- 

 tremity two caudal appendages, slightly ciliated on the 

 lower margin, and varying in size in the two sexes. In 

 the female they are much smaller than in the male, and 

 she has tAvo long oviferous tubes, such as the Caligi pos- 

 sess, much longer than the whole body of the animal, and 

 arising near the posterior edge of the last segment of the 

 thorax. The anterior portion of the carapace possesses, 

 like the Caligidae, the small, narrow, transverse frontal 



