364 KEY. T. B. K. STEBBING ON NEW SPECIES OF AMPHIPODOUS 



The second antennae have at the base two short stout joints. The third is longer 

 and more slender than either of these, and the fourth than the third, with a slight 

 dilatation near the middle. The fifth joint is more slender than the fourth, but quite 

 as long. The four remaining joints are together somewhat longer than the preceding 

 joint. This form is no doubt a stage in the development of the antennae of the male. 



The gnathopods differ little from those of Scina siviilis. There are branchial vesicles 

 attached to the second gnathopods and to the first four pairs of peraeopods. 



In the first and second peraeopods the fifth joint is longer than the fourth or the 

 sixth. The finger is much curved. 



The third peraeopods have twelve teeth on the hind margin and about the same 

 number on the front, together with an apical tooth longer than the third joint. The 

 fourth and fifth joints are subequal in length ; together they are as long as the second 

 joint apart from its apical tooth. The sixth joint is rather shorter than the fifth. The 

 finger is minute, triangular, its apex forming a nail. 



The fourth peraeopods are shorter than the first or second. They have the fourth 

 and fifth joints equal, the sixth shorter than the fifth and a little shorter than the 

 corresponding joint in the preceding pair, while the finger is similar to that of the 

 third pair, but rather stouter. 



The fifth peraeopods are robust, with the fourth joint longer than the fifth, and the 

 fifth than the sixth. The finger is curiously shaped, thick at the base, then narrowing, 

 and again widening, the widened extremity being closely beset by a pair of spines or 

 sort of double nail. 



The pleopods have nine joints to the outer and seven to the inner branch. 

 The first uropods reach beyond the second, nearly to the extremity of the third. 

 They have the peduncle rather shorter than the inner branch, of which the outer margin 

 is minutely serrate ; there are teeth sparsely set on the inner margin of both peduncle and 

 branch. The outer ramus is a small thick spine. The second pair reach nearly as far 

 as the outer branch of the third pair; they have the peduncle rather shorter than the 

 inner branch, which is finely serrate on its inner margin ; the outer branch is a little 

 longer than in the first pair. The third pair have the peduncle nearly as long as the 

 outer branch, which is fully four-fifths as long as the inner ; the confronting margins 

 of the two branches are serrate. 



The specimen measures three-tenths of an inch. 



Habitat. Atlantic. Lat. 7° 54' N., long. 17° 25' W. Taken between C and 7 p.m. 

 from a depth of 50 fathoms. 



The specific name refers to the peculiarly hooked finger of the fifth peraeopods. 

 From the more or less nearly related species, fScina marginata (Bovallius) and Sdna 

 lepisma, Chun, it is separated not only by the finger in question, but by the hands of 

 the gnathopods, which are not apically produced into a sharp process. 



