56 TIIK \OYA(iK OF H.M.S. (;HALLENGErv. 



iVlthough the present species would seem to l)e widely distiilmted, and a ratliei- 

 plentiful .sujiply of specimens was colleftcd by the Challenger Expedition, it has 

 proved a matter of no small difficulty to make out its anatomy and to arrive at a correct 

 idea of the general appearance of the animal, most of the specimens, owing to their great 

 fraoilitv, beino- in a ratliei' imperfect state of preservation, and having lost a more or less 

 considerable numl>cr of their limbs. Plowever, by comparing all the specimens, and 

 supplying from one what is wanting in another, I have finally succeeded in attaining 

 a tolerably complete knowledge of the organisation of this remarkable Crustacean, and at 

 the same time have l)een enabled to confirm the statements of the late Dr. v. Willemoes- 

 Suhm, as to certain important characteristics omitted in the description given by Dana. 



Description. — The length of the largest specimen, a female with remarkably 

 developed marsupial ])0uch, is 50 mm. 



All the integuments are very thin and soft, almost membranous, and hence the 

 o-eneral form of the bodv has in most cases been somewhat altered bv the action of the 

 spirit or by accidental pressure. 



In the best preserved specimens, the body exhibits (see PI. IX. figs. 1,2; PI. X. 

 fig. l) a rather slender form, the anterior division lieing almost cylindrical, the posterior 

 tapering rapidly towards the end. 



The carapace is very large, and, as in Gnathbphausia, connate with the body in its 



most anterior part only, but otherwise loosely covering the trunk, all the segments of 



which are distinct!)' defined in their whole circumference (see PL X. fig. 2), the last 



being perceptibly larger than the others. It is deeply emarginate posteriorly, mthout, 



however, as stated by Dana, leaving any of the segments of the trunk uncovered. The 



lateral wings are rather jiroduced, and rounded at the tip, extending laterally along the 



anterior part of the tail and reaching far bej^ond its first segment, in some specimens 



almost to the end of the second (see PL IX. fig. l). The inferior margins, too, are very 



slightly arcuate, covering in part the bases of the legs, and terminating anteriorly in 



an obtuse angle. The anterior part of the carapace exhibits above an indistinctly 



areolate appearance, two transverse depressions, one of which may l)e the cervical 



sulcus occurring here, partly crossed by a slight longitudinal depression on either side. 



Moreover, the l)rauchiostegal line, marking off the linguiform dorsal area, is distinctl\- 



perceptil)lc (see PL IX. figs. 1. 2). The frontal margin is evenly curved, not 



forming any rostral jirojection, and leaving the ocular segment uncovered. Beneath 



and somewhat external to the eyes, on either side, a slight projection is seen, apparently 



corresponding to the infra-orbital spine in other Podophthalmians. On the other hand. 



no trace whatever c;in be found of either supra-orbital or of nutcnnal and In'anchiostegal 



spines. 



The caudal segments do not exhibit any distinctly developed epimera, being evenly 

 rounded both ventrally and dorsally. They rapidly diminish in l^readth posteriorh', and 



