352 EEV. T. E R. STEBBING ON NEW SPECIES OF AMPHIPODOUS 



of size. Without taking into account other features, such as the eyes and the 

 telson, or the general shape and armature of the body, it may be left to the 

 arithmetician to calculate, if he can, how many species may be framed from the given 

 conditions. Some praise should be allowed to the moderation of nature and of 

 naturalists, in that, with such facilities at command, they have been contented as yet 

 with creatino- only twenty-one species in the genus, including in that number all the 

 doubtful names and seven new species instituted in the present paper. Probably not 

 more than fifteen of the twenty-one can be sustained. Of these there are some which 

 can only be distinguished from one another by close comparison of various details, but 

 Scina marginata (Bovallius) is at once marked out by having the apex of the hands in 

 the onathopods produced. No other species, unless Scina lepisma be distinct from Scina 

 marqinata, shares this peculiarity. Scina acanfhodes, n. sp., is unique in the dentate 

 armature of the perseon and pleon. Scina stenojms, n. sp., is unique in the enormous 

 elongation of the peduncles of the uropods, only the otherwise very different Scina 

 acantJiodes making any approach to it in this respect. Bovallius considers the Scina 

 cornigera of Milne-Edwards uniquely devoid of outer branches to the third uropods ; but 

 in that case I take it for granted that they were present though not observed, such an 

 oversight easily occurring when the more striking features of the animal Avere attracting 

 attention by their novelty. Scina imcipes, n. sp., is unique in the blunt-ended finger of 

 its fifth perseopods, though it agrees more or less with Scina mai'ginafa in the unwonted 

 thickness of those limbs. The species at large may be roughly divided into two groups 

 — one in which, as in Scina cornigera, the first antennae are of very great length, the 

 other in which, as in Scina horealis, they are of much more moderate extent. In 

 the determination of species it is useful also to note whether the second joint of the 

 third perieopods is dentate on both sides or only on one, and whether the finger of the 

 fifth perseopods is hooked or simple. The serrature or denticulation of the margins of 

 the uropods varies in different species, but the details are often microscopic. The 

 number of species is at present rather surprisingly large compared with the number of 

 specimens known. They have been instituted on the supposition that the proportional 

 sizes of the antennae, of the joints of the limbs, and of the uropods are fairly constant 

 for each species. Should this supposition prove unsound, a further revision would 

 doubtless be required. As the list at present stands, if it be right to cancel for different 

 reasons the names crassicornis, gracilis, longipes, sarsi, lepisma, and to leave ensicorne 

 in suspense, the species i-emaining will be cornigera, Milne-Edwards, horealis, atlantica, 

 clausi, marginata, tullhergi, and pacijica of Bovallius, bovallii of Chun, and acanthodes, 

 stenojpus, oedicarpus, rattrayi, concors, similis, and uncipes of the present paper. 



Scina acanthodes, n. sp. (Plate LI.) 



The head in front is deeply emarginate, forming two blunt lobes, behind which it is 

 dorsally traversed by a curved line. The perseon increases in width to the fourth 



