50 THE VOYAGE OF H.M.S. (IHALLENGER. 



Altlioiioh the preseut sjjecies woulJ seem to lie widely distributed, and a ratlier 

 plentiful supply of specimens was collected \>y the Challenger Exjjedition, it has 

 proved a matter of no small ditiiculty 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 

 fragility, being in a- rather imperfect state of preservation, and having lost a more or less 

 considerable nnmber of their liml)s. However, 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 been enabled to (-(infirm the statements of the late ])r. v. Willemoes- 

 Suhm, as to certain imjiortant characteristics omitted in the descrijition given liy Dana. 



Deficription. — The length of the largest sjiecimen. a female with remarkably 

 developed marsupial jiouch, is 50 mm. 



All the integuments are A'ery thin and soft, almost memliranous, and hence the 

 general form of the body has in most cases been somewhat altered liy the action of the 

 spirit or liy accidental pressure. 



In the 1iest preserved specimens, the liody exhiljits (see PI. IX. figs. 1, 2 ; PI. X. 

 fig. 1) a rather slender form, the anterior division being almost cylindrical, the posterior 

 tapering rapidly towards the end. 



The carapace is very large, and, as in (riai-thoj^hausta, connate with the IkmIv in its 

 most anterior ]iart only, liut otherwise looselv covering tlie trunk, all the segments of 

 which are distinctly defined in theii' wliolc circumference (see PI. X. fig. 2), the last 

 being iierceptibly larger than the others. It is deeply emarginate posterioi-lv, without, 

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

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

 anterior part of the tail and reaching far l)eyoud its first segment, in some specimens 

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

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

 an (ilituse angle. The anterior part of the cara}iace exhiliits above an indistinctly 

 areolate apjiearance, two transverse depressions, one of which may be the cervical 

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

 Moreover, the branchiostegal line, marking oft' tlie linguiform dorsal area, is distinctly 

 percejitible (see PI. IX. figs. 1, 2). The frontal margin is evenly curved, not 

 f( liming any rostral jirojection, and leaving the ocular segment uncovered. Beneath 

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

 corresponding to the infra-orliital spine in other Podophthalmians. ( )n the other hand, 

 no trace whatever can be found of either supra-orbital or of antcnnal and liranchiostegal 

 spines. 



The caudal .segments do not exhibit any distinctly developed e])imera, being eveidy 

 rounded botli ventnilly a.nd dorsally. They rapidly diniinish in breadth jiostcriorly. and 



