ALLOUCliESTES NlLSSONll. 41 



The eyes are not large, but round and black. The 

 superior antennae reach to the extremity of the peduncle 

 of the inferior. The inferior antennae are about one- 

 fourth the length of the whole animal, with the peduncle 

 about half the length of the antennae. The two basal 

 joints are closely incorporated, but not fused, with the 

 head. The mandibles are short, denticulated at the 

 margin, furnished with a secondary plate, but destitute 

 of any palpiform appendage. The foot-jaws are fur- 

 nished at the apex with a sharp nail. The squamiform 

 plates are three, two important, the third less so, fringed 

 with short hairs. The first pair of legs have the hand 

 oval, or nearly so, when the finger is shut : the palm is 

 convex, and an obtuse tooth is placed just beyond the 

 apex of the shut finger : the wrist is moderately pro- 

 duced inferiorly. The second pair of legs have the hand 

 much more developed, but formed upon the same type 

 as the first. All the other pairs of legs terminate in 

 curved pointed fingers. 



The squamiform basal joint of the four anterior pairs 

 of limbs is as broad as deep, and nearly as deep as 

 the respective segment of the body to which it is at- 

 tached. Those belonging to the three posterior pairs 

 are much shorter. The caudal appendages are short, 

 stiff, and furnished with short, spine-like hairs. The 

 middle tail-piece is single and small. 



This animal has, no doubt, been mistaken for the 

 young of Orchestia littorea, to which it bears a general 

 resemblance ; but it can readily be distinguished by the 

 length of the superior antennae, which are rather stiff in 

 their general appearance. 



The microscopic structure of the skin shows a distinc- 

 tion (although not a very great one) from that of Talitrus 

 and Orchestia. The t- markings are somewhat more nu- 



