ISOPODA. 



59 



fourth shortest, subequal in length ; the second and third also subequal, but little 

 longer. All straight, the first partially enclosing the cephalosome-. The three posterior 

 segments subequal in length, increasing in curvature and decreasing in breadth to the 

 last. Lateral margins of all the segments more or less truncated, the first three 

 obliquely so, and all with distinct epimera, triangular in shape. 



Metasome, a single small segment wedged in the curvature of the preceding 

 segment, and a urosome, large vaulted, fringed, but not thickly with spinous sette, and 

 which form two small groups distally. Veutrally it forms a pocket for the pleopoda. 

 In shape the urosome varies largely, in the smaller specimens it is ovoid with a slight 

 depression for the reception of the diminutive uropoda. In the old adult males it 

 becomes globular, with a truncated projection distally armed with two small groups 

 of spines. 



The males resemble the females, except that the latter are very much broader and 

 the mesosome ovoid. 



First antenna, the short peduncle is two-jointed. The first joint is short and stout, 

 the second is slender and a little longer ; the multi-articulate flagellum is about half as 

 long again as the peduncle. 



Second antenna, very long, peduncle six-jointed. The first three joints are very 

 short, the second being as long as the other two together, and constricted in the 

 middle ; the other three joints are long, the fourth is long, the fifth much shorter 

 and armed distally with a spine ; the sixth is simply enormous, longer than the two 

 preceding together. It is very slender, and provided with setae throughout. The 

 multi-articulate fiagellum is longer than this joint. 



Mandible. Strong, curved, cutting edge with two long teeth anteriorly, a third 

 with which is associated a group of spinous setae. Molar tubercle very prominent, 

 its edge produced to a fine point posteriorly. Palp three-jointed, second joint a 

 little the longest, the other two subequal ; the second joint has two, and the terminal 

 one three or four stout setae armed with very fine closely set teeth. 



First maxilla. Normal, the inner lobe terminates in three spinous setae and a 

 smaller one ; these are coarsely plumose, at least on one side. External to these is a 

 group of finer setae. The outer lobe has about ten stout pectinate spines distally, 

 another row of them internally, a short distance below. A group of much finer 

 ones occurs on the inner edge of the joint. 



Second maxilla. Normal, a rather broad blade reduced to about half its diameter 

 in the distal half. This portion forms a blade, the inner and distal margin of which is 

 thickly covered with stiff' setae. The external joint is bifurcated, the inner part being 

 the stouter, both terminate with four long setae. 



Maxilliped. A short basal joint, the masticatory lobe is two-jointed, subequal in 

 length. The distal joint is rounded externally and armed at its extremity and 

 internally with coarsely plumose setae. The inner margin carries four papilliform 

 teeth about the middle of its length. The palp is five-jointed, the first short, the 



p 2 



R A h 



- 



