ISOPODS OF NORTH AMERICA. 



277 



FIG. 288. TECTICEPS ALASCENSIS. a, MANDIBLE. 

 b, MANDIBULAK APPENDAGE, x 5J. c, MAX- 



ILLJPED. X 20J. 



broad plate at the side of the segment. The epimera of all the seg- 

 ments are about twice as broad as long, with the exception of those of 

 the fifth segment, which are nearly 

 square and very conspicuous. 



The first segment of the abdomen 

 has three suture lines, and its pos- 

 terior margin projects down in two 

 small triangular processes, on? on 

 either side, over the terminal seg- 

 ment. The terminal segment is tri- 

 angular, and has a very pointed 

 extremity. The branches of the 

 uropods differ considerably. The 

 inner one is broad and tapering, 



and does not reach the tip of the abdomen. The outer one is slender 

 and sharply pointed, and extends be} r ond the abdomen. 



The first pair of legs are subchelate, as 

 are also the second pair in the male. In 

 the first pair the propodus is large and 

 oval in shape, and bears in the palma a 

 row of stiff bristles at regular intervals 

 and pointing obliquely in the same direc- 

 tion, while a thick row of fine cilia, point- 

 ing obliquely in the opposite direction, 

 crosses these almost at right angles. The 

 dactylus terminates in a single hook, at 

 the base of which two smaller hooks are 

 situated. In the legs of the second pair 

 the propodus is irregular in shape with an 

 indication of a rudimentary pollex. There 

 are no hairs or bristles in the palma. The 

 legs of the third, fourth, and fifth pairs 

 present nothing unusual in structure, but 

 resemble the ambulatory legs common to 

 this family. In the sixth and seventh 

 pairs the structure is the same as that of 

 the preceding legs of the third, fourth, 

 and fifth pairs, but with an increasing 

 disproportion in the length of the propo- 

 dus and dactylus. In the seventh pair of 

 legs these joints, but more especially the 

 propodus, attain a size most conspicuous 

 for their length. The propodus becomes 

 over 3 times longer than the carpus which immediately precedes it. 

 Color. The color varies from dark brown to yellow, more or less 



FIG. 289. TECTICEPS ALASCENSIS. a, 

 LEG OF FIRST PAIR, x 5|. 6, LAST 



TWO JOINTS OF SAME. X lOf . C, LEG 

 OF SECOND PAIR OF MALE. X 6f . d, 



LEG OF THIRD PAIR, x 5}. e, LEG 



OF SIXTH PAIR. X 6|. /, LEG OF 

 SEVENTH PAIR. X 5|. 



