THE ISOPOD QEKUS OUJiOZEUKTES. 335 



The underside of the abdomen I have not been able, in the 

 single specimen in question, to examine in detail. It is, how- 

 ever, possible, by turning back the last pair of oostegites, to see 

 the end of the thoracic steruites, here soft, with a little chitinous 

 matter and a marked conical central papilla (PI. XIV". fig. 9). 



Behind this the thoraco-abdomiual suture is evident, and the 

 bases of the first fair of abdominal afpendages are large and 

 prominent. 



The basal joint is bilobed, and bears the large curved plate 

 whichi v\e have already noticed as overlapping the dorsal sur- 

 face of the abdomen above and covering its ventral aspect. Its 

 central region is more strongly calcified than the flexible mem- 

 branous borders. 



The inner angle of the basal segment bears also a true gill- 

 plate lying over (ventral to) those of the succeeding four pairs of 

 appendages, and resembling in form and structure the third 

 lamella of appendages two to five. 



The typical aldominal appendage, such as is found on segments 

 two to five, has a short basal joint, moderately calcified and 

 imperfectly subdivided, bearing three perfectly distinct lamellae 

 (PJ. XIV. fig. 10). 



On the outside (ventral surface) is a delicate square plate 

 attached to an outer calcification of the basal segment ; it is 

 very thin in texture, and the anastomosing blood-vessels are 

 plainly visible. 



The middle or largest lamella is triangular in outline, and 

 attached to the main portion of the basal joint : a glance at the 

 dorsal surface shows, however, that it is not attached along the 

 whole of the base, but only at a middle point in a deep sinus, so 

 that its basal margin is markedly cordate. 



The third or smallest lamella is less than half the size of the 

 last, of an oval shape, pointed at the distal end, and attached in 

 the proximal region between two unequal forwardly extending 

 lobes ; so that it has the same cordate base as the middle lamella, 

 but more irregular. 



The third, fourth, and fifth abdominal appendages are all 

 constructed on the type of the second, Avhich I have chosen 

 for description. 



The sixth pair, which are so prominent in the larva, still retain 

 the same structure — a basal joint with two flattened lamellae. 

 In the adult, however, the lamellae are almost equal in size, 

 narrow in proportion to their length, and devoid of setae. The 



