MUSEUM OF COMPARATIVE ZOOLOGY. 33 



The antennal scale is about as long as the sixth segment of the abdomen and 

 about twice and a half as long as broad, and the ultimate segment of th6 pe- 

 duncle reaches very nearly to the tip of the scale. 



The external maxillipeds are much more slender than in C. borcas and reach 

 by the tips of the antennal scales about half the length of the ultimate segment, 

 which is no broader than the penultimate but fully twice as long and about six 

 times as long as broad ; the antepenultimate segment is longer than the ultimate. 



The thoracic legs are nearly as in C. boreas, but are all rather more slender 

 and less hairy. In the first pair the carpal spines are smaller and the chelae 

 are nearly naked and less swollen than in C. boreas. The second pair are 

 nearly as long as the first : the carpus and merus are subequal in length, and 

 each is a little longer tlian the ischium ; the chela is ver}'- slender, about hali' 

 as long as the carpus, with the digits scarcely a third as long as the basal j^or- 

 tion of the chela. The third pair are about as long as the second, the carpus a 

 little longer than the merus, the propodus two thirds as long as the carpus, and 

 the very slender dactylus but little less than half as long as the propodus. The 

 fourth pair do not quite reach the tips of the third, and the fifth reach slightly 

 by the carpi of the fourth. 



The abdomen is broad, slightly depressed and rounded above anteriorly, and 

 tapers rapidly to the sixth somite, which is only a little longer than the fifth. 

 The five anterior somites are armed with a median dorsal carina which is con- 

 Bpicuous and flattened above on the fourth and fifth. The epimeron of the first 

 somite is broadly expanded anteriorly and projects in an obtuse tooth below ; 

 the second is broad and evenly rounded in front and behind, and has a slight 

 tooth below, but the inferior edges of the remaining epimera are straight and 

 unarmed. The sixth somite, excluding spines, is about a fourth longer than 

 the fifth, is armed above with four prominent and approximately equidistant 

 carinse, and the posterior edge projects in a large tooth either side of the base 

 of the telson and in an acute angle at the lateral margin. The carina) and the 

 teeth on the edges of the epimera are more prominent in the male than in the 

 female. 



The lamella; of the uropods are much shorter than the telson : the outer are 

 from a little more than twice to about three times as long as broad ; the inner 

 are about as long as the outer, and three to four times as long as broad. 



The telson is about once and two thirds as long as the sixth somite of the 

 abdomen, flattened and broadly channelled above, tapers regularly to an acute 

 point unarmed with spines but furnished with two pairs of plumose setae aris- 

 ing from the under side, and the margins are ciliated beneath. 



In the male there is a very long median spine on the sternum of each of the 

 four anterior somites of the abdomen, but no similar spines in the female. 



The surface of the carapax and abdomen is sparsely clothed with minute pu- 

 bescence, which is very easily removed with the coating of soft mud with which 

 all the specimens are covered. 



The number and arrangement of the branchiae is the same as in C. boreas, 

 and as indicated by the following formula : — 



VOL. X. — NO. 1. 3 



