12 T. V. HODOSON. 



generally has a very obvious depression in the centre. The next, or fifth segment, is 

 the longest, and there is a progressive increase in length from the first to the fifth, 

 this one hears more or less distinct traces of a median longitudinal division. The 

 sixth segment is a little shorter than the preceding, and posteriorly it terminates in- 

 three lobes, the median is short and the width of the abdomen, the lateral ones are 

 large and project along the sides of that structure. The last segment of the mesosome 

 is much reduced in size and almost fills the interval between these lobes. Laterally 

 the second and third segments of the mesosome are covered with small spines or 

 tubercles, a feature which is not brought out in the figure in the ' Southern Cross ' 

 Report. The ccphalon and every segment of the thorax bears laterally a number of 

 long slender setje. A feature which is not alluded to in the original description is 

 the crustaceous character of the exoskeleton, this is usually very prominent down to 

 and including the fifth thoracic segment, although it is to a certain extent covered by 

 a mass of diatomaceous matter. The posterior segments of the thorax and the 

 abdomen are almost invariably thickly covered with a similar growth, often so much 

 as to completely conceal all structural details. 



The metasome consists of six joints of sul»equal size, the telson, a pointed 

 triangular structure with a few long setfe distally being fused with the last one. The 

 epimera are broad blades, curved to a slight extent backwards. The last abdominal 

 segment has no epimera. The uropoda are well developed, the basal joint is short 

 and stout, the two rami are subequal in length, but the endopodite is considerably 

 broader than the exupodite, l)oth are fringed distally witli long setiu and have three 

 shorter ones on their external borders. 



The first antenna consists of a three-joiuted peduncle and a short, four-jointed 

 flagellum. The first two joints of the peduncle are short and suboqual, the third is 

 hmger than the other two together, all bear a few setae distally. 



The second antenna comprises a peduncle of four joints and a flagellum of six 

 or thereabouts. The first two joints of the peduncle are short, the third is about as 

 long as the two preceding ones together, and the fourth is still longer ; this one 

 carries along the side of it a sei'ies of seta; of increasing length. 



The mandible is scythe-like in general appearance, the amount of curvature of 

 the free end being variable, the outer margin carries a sharp spur near its middle, and 

 the inner cutting edge is slightly sinuous. 



The niaxilliped is a small structure, the liasal plate is rather large, comparatively 

 roughly triangular and attached by its truncated apex. The masticatory process is a 

 .small clavatc process bearing two stout knobbed processes on the inner side. The 

 palp consists of four .small rounded joints which taper slightly from the first, and each 

 carries a few long .setae on the outer margin. 



Tlie gnathopod is a large pyriform spoon-like structure forming an operculum 

 over the residuum of the mouth organs. It is attached on one .side near the base 

 and its rounded free margin is fringed witli dclicatclv jilumosc sct;v. Its surface is 



