8 PROF. M. M. HAETOG ON THE 



Male. Female. 



Length of carapace 505 fi 726 /x, 



Length from rostrum to end of thor. v. . 863 ft 1242/4 

 Length from thor. vi. to abd. iv. inclusive! „ QQ KAQ 



(hind body excluding furca) . . . ./ dyy/i 548 ^ 



Length of furca 126 /x 210 fi 



Longest furcal spine (taken between two") p- fi Q „„« 



transverse parallels) J " ^ 



Total length 1946 /j, 2726 /x 



Greatest width 484 fj, 684 p 



Width : length 10 : 40 10 : 39 



The proper trunk-muscles are not very complicated; they fall into two groups, 

 extensors and flexors. In the fore body, the great extensors of the body form two 

 symmetrical groups taking origin at the anterior lateral portion of the carapace (below 

 and external to the muscles of the antennules and antennae) and are attached chiefly to 

 the anterior edges of the third and partly the fourth thoracic segment. Mediad of these 

 a series of small extensors form V's with the apex backwards, running from the anterior 

 edges of the third, fourth, and fifth segments to those in front of them, the muscles 

 running over most segments being external. Two pairs of these extensors go from the 

 dorsal region of the carapace to the second (first free) thoracic segment — one anterior 

 starting from just above the great extensors ; the other internal and posterior from 

 about the level of the maxillipeds. 



The great flexors (PI. II. figs. 4 & 5) take origin on the upper edge of the " leg" and 

 posterior edge of the " foot " of the postmaxillary apodeme, and converge with inter- 

 segmental tendinous intersections on the ventral surface (which, however, do not extend 

 through the whole thickness of the muscle), and are inserted partly into a pair of apo- 

 demes on the sternal region of the fourth thoracic segment, near the middle line and 

 posterior to the limbs ; but their chief insertion is into a median peg-like apodeme on 

 the incomplete sternal ring of chitin forming the hinder limit of the fifth (or anterior 

 detached piece of the sixth ?) segment ; while the outer part of these flexors appears to 

 become continuous with those of the abdomen. 



In the hind body the muscles are divided into four groups, two super o-lateral and two' 

 infero-lateral, the uppermost of the former group acting as extensors, and the lowermost 

 of the latter as flexors. Here all the muscles are parallel, and the nearer the middle 

 line the shorter their course, just as in the dorsal thoracic region. No muscles extend to 

 the furca. 



A series of short pleural muscles connect the two walls of the pleura together, 

 especially visible in transverse sections of the carapace. The other body -muscles belong 

 either to the limbs or to the visceral system, and will be described with them. 



The paired appendages are confined to the cephalothorax (unless we regard the furcal 

 processes as such) and are eleven in number : antennules, antennae, mandibles, maxilla? 

 of first pair, maxillae of second pair (of which the rami are discrete to the very base, so 

 that they are conveniently and commonly described as outer and inner, or anterior and 

 posterior maxillipeds), four pairs of oar-feet, and two pairs of rudimentary feet, the 

 hinder of which serve the purpose of genital valves. The only sexual differences to be 

 noted are in the antennules and the genital valves. 



