GAMMARHXaB. 



tail are armed with a central dorsal tooth, directed pos- 

 teriorly. The eyes are kidney-shaped. The antennae 

 are short, being scarcely one-sixth the length of the 

 animal. The first pair of legs are slender and weak, 

 with the finger obsolete. The second pair of legs are 

 scarcely stouter than the first, and terminate in an im- 

 perfectly chelate organ. The walking legs are tolerably 

 robust, and differ from those of /. obesa only in having 

 the thighs of the last three pairs produced posteriorly 

 in two sharp points or teeth. The last three pairs of 

 caudal appendages are nearly of the same length, and 

 the central tail-piece is emarginate at the apex. 



Several specimens of this species were taken by Pro- 

 fessor Kinahan, from the branchial cavities of Rhizostoma 

 Cuvieri. The specimen from which our figure and de- 

 scription were taken is preserved, in an imperfect state, 

 in the Dublin Museum. M. Guerin-Meneville had some 

 specimens in his collection, procured on the western 

 coast of England. 



The circumstance of this animal having been found 

 inhabiting the gill-cavities of a Medusa establishes 

 another link associating this subfamily more closely 

 with the Hyperina than was at first presumed. 



