316 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



subcircular pleon. From the terrestrial forms, which it somewhat re- 

 sembles, and iu company with which it may sometimes be found, the 

 above-mentioned character, joined with the miiltiarticulate flagellum of 

 the antennae, will serve to distinguish it. 



The body is oval and flattened, a little more than twice as long as broad. 

 The head is transverse, broadly excavated on each side over the bases of 

 the antennulae, sparingly ciUated on the lateral margins, with short scat- 

 tered spine-like unequal cilia or sette, which occur in a similar manner 

 along the entire borders of the animal behind the front margin of the head. 

 The eyes are prominent and black, situated near the posterior margin 

 of the lateral regions of the head. The antenuulae are five-jointed, and 

 do not surpass the fourth segment of the antennae ; the basal segment 

 is large and separated from its fellow of the opposite side by about 

 twice its diameter ; the second segment is about as long as the first, but 

 of much less than half its diameter ; third segment shorter than the 

 second, fourth still shorter, fifth tapering, tipped with setae. The first 

 three segments of the antennae are short; the fourth is robust, and 

 about as long as the first three together ; the fifth is longest, and is fol- 

 lowed by a slender elongated flagellum. The maxillipeds (pi. I, fig. 

 6) have the external lamella (1) short and broad, nearly straight on the 

 inner margin, broadly rounded at the end, and somewhat swollen on 

 the external side; the palpus (j)) is five-jointed; the first three segments 

 flattened, first short ; second dilated internally and ciliated ; third ciliate 

 in the inner margin and narrowed to the base of the fourth segment, 

 which is cylindrical ; fifth short, conical. The terminal lobe of the max- 

 illiped bears two rows of cilia near the apex, and on the inner side a row 

 of short styliform organs. The outer maxillae (pi. I, fig. 6 a) consist of 

 a semioval portion, broad and ciliated at the tip, bearing above the 

 middle two articulated lobes, armed with strong curved setae at the tip. 

 The inner maxillae (i)l. I, fig. C h) are armed with short stout spines, which 

 are strongly spinulose on their inner curved side ; inner lobe about half 

 the diameter of the outer. Mandibles with a very much projecting molar 

 process, a comb of pectinated setae, and a dentigerous lamella, or two of 

 them on the left side. 



The first three thoracic segments are of about equal length along the 

 median line, and are together nearly equal in length to the last four, 

 which are also subequal along the median line, but the fifth segment 

 appears shorter than the others on account of its short lateral margin, 

 which has both its anterior and posterior angles stronglj^ rounded. The 

 epimeral region of the segments projects at the sides so as to cover the 

 bases of the legs, and is squarish in the first three segments, rounded in 

 the fourth, and still more so in the fifth, and obtusely angulated behind 

 in the sixth and seventh. The legs are similar in form throughout, but 

 increase in length to the last pair. They have the basis rather robust j 

 the ischium shorter and flexed on the basis ; the merus subtriangular, 

 and tipped with spines ; the carpus and propodus cylindrical, subequal 



