652 THE VOYAGE OF H.M.S. CHALLENGER. 



a well-defined circular spot, or little eye, distinct from the primary organ. In Plcsionika, 

 Pandalopsis and Pandalus it is not conspicuous, but a process of the pigment extends 

 beyond the margin as if it were an incipient condition of the more complete ocellus 

 found in this genus. 



In this genus, as distinguishing it from Pandalus, the stylocerite is sharp pointed 

 and the flagella of the first pair of antennae are long and slender, being as long as or 

 longer than the rostrum or the carapace. 



The mandibles are formed much like those in the genus Heterocarpus, in having the 

 molar process cylindrical, and projecting at right angles to the apophysis ; at the angle 

 so formed the psalistoma and the three-jointed synaphipod projects. 



The oral appendages resemble generically those of Heterocarpus, but in Pandalus 

 the mastigobranchial plate of the second siagnopod extends backwards into the branchial 

 chamber, and by means of the long terminal hairs at its distal extremity brushes all the 

 plumes, whereas in Nothocaris, as in Plesionika, it terminates abruptly in a rounded 

 extremity fringed with fine cilia, and does not extend into the branchial chamber. 



The first pair of gnathopoda has the propodos long, broad, and reflexed against the 

 meros, and the dactylos broad and continuous with the propodos. 



The second pair of gnathopoda is five-jointed and pediform ; the first joint or coxa 

 carries a rudimentary mastigobranchia, at the base of which a flattened calcified disc 

 projects at right angles ; the basis is short and carries an ecphysis that is long, narrow, 

 and about half the length of the ischium or succeeding joint ; the ischium is long and 

 has the margins parallel and fringed with tufts of hairs. The next joint is shorter, being 

 not quite half the length of the preceding, and the terminal is longer but not quite so 

 long as the ischium ; it is cylindrical, and furnished at the extremity with two or three 

 strong spines, and along the outer margin with a series of tufts of hairs, mingled with a 

 few spines. 



The first pair of pereiopoda is long, slender and pediform ; the coxa carries a small 

 mastigobranchia, and is furnished with a tuft of long hairs on a prominent tubercle ; the 

 basis is short and carries no ecphysis ; the ischium is long, but not so long as the meros, 

 with which it is connected by an oblique articulation, and it becomes slightly narrower 

 towards the distal extremity, where it articulates with a long carpos ; the jiropodos is 

 straight and cylindrical, about half the length of the carpos, and is furnished at the 

 distal extremity with a lanceolate point, which appears to represent a rudimentary 

 dactylos anchylosed with it, and carries on its under surface a tuft or two of long hairs, 

 directed backwards. The second pair of pereiopoda is long and slender, the carpos being 

 multiarticulate and longer on the right side than the left. The posterior three pairs of 

 pereiopoda are longer and more slender than in Heterocarpus, corresponding more with 

 those of Plesionika, and are, moreover, furnished with spines on the posterior margin of 

 the meros and ischium, which, however, are less numerous and not so large. 



