On Stenocypris Chevreuxi. 9 



the inner cavity of the shell, and that sufficient room is 

 left for all the appendages, when drawn in by the animal 

 on closing its shell. During the movements of the animal, 

 however, both pairs of antennæ, as also generally the anterior 

 pair of legs, and at times the caudal rami are seen 

 to extend from the shell. The body is attached to the 

 shell along the whole dorsal face and also laterally by the 

 great adductor muscle, in such a manner, that only its 

 hindmost part is freely movable within the shell. In front 

 the body appears, as it were, transversely truncated, and 

 any boundary between the head and trunk does not exist, 

 nor is the abdominal division defined from the trunk by 

 any intervening suture or constriction. There is consequently 

 no distinctly pronounced segmentation of the body, and the 

 number of segments that originally compose it, can there- 

 fore only be determined by the number of limbs. This 

 is rather restricted, being only 7 pairs in all, viz., 2 pairs 

 of antennæ, 1 pair of mandibles, 2 pairs of maxillæ, and 2 

 pairs of legs. Quite in front, and at a short distance from 

 the dorsal face, the eye occurs, and may also be fairly well 

 traced through the shell. Immediately beneath it, the superior 

 antennæ issue, acting, during the motions of the animal, 

 upwards and backwards. At some distance below them, the 

 doubly-geniculated inferior antennæ originate, acting in 

 an opposite manner to the superior ones, viz., downwards 

 and backwards. Between the bases of those antennæ the 

 voluminous anterior lip is seen to project, forming in front 

 an obtuse prominence. The oral aperture is found ventrally 

 at a considerable distance from the bases of the inferior 

 antennæ, and on the sides of it are seen the bodies of the 

 mandibles, with their masticatory parts wedged in between 

 the anterior and posterior lips, whereas their distal parts 



