268 Messrs. J. Wood-Mason and A. Alcock on 



continued to the posterior margin of the carapace ; its spines 

 are larger, more compressed, and less inclined, though more 

 curved, than those of the rostrum, and subequal, with one or 

 two shorter and slenderer ones intercalated between them here 

 and there. In addition to the dorsal ridge the cara])ace bears 

 on each side four other longitudinal rows of spines : the first 

 of these runs quite close and subparallel to the dorsal ridge 

 from one end of the carapace to the other ; the second com- 

 mences with the antennulary spine, curves slightly down- 

 wards and then slightly upwards to the cervical suture, 

 whence it takes a straight course to the hinder margin, rutming 

 parallel to the dorsal ridge; the third consists of tlie antennal 

 spine and of two spines on the posterior half of the cephalic 

 portion of the carapace ; the fourtii, of five or six spines com- 

 mencing with the branchiostegal spine, and runs along the 

 middle of the prominent efferent branchial canal, and like the 

 second has its spines connected by a ridge. 



The surface of the part of the branchiostegite coinciding 

 with the subjacent branchial chamber is raised into a longi- 

 tudinally oval convex-topped elevation, which is fringed at 

 the edges %Aith strong spines and bears an irregular row of 

 five or six along its middle. Between the branchial eleva- 

 tion and the almost horizontally inflected portion of the cara- 

 pace are some smaller spines roughly in the same straight 

 line with those on the efferent branchial canal. 



The abdomen is armed along the middorsal line with a 

 spiniterous ridge similar to that of the ceplialothorax and 

 extending almost without interruption from the base to the 

 apex, bemg absent only in the basal half of the fifth tergum, 

 on the sides of its terga and pleura with symmetrically 

 arranged spines similar in form to those of the dorsal ridge, 

 and on the edges of each of its pleura with several ex- 

 ceedingly long and slender needle-like spines, besides smaller 

 ones ; tlie number, form, arrangement, size, and direction of 

 these spines, which vary within small limits in all of the 

 above respects from specimen to specimen, will be best under- 

 stood by leference to the accompanying figures. The first 

 abdominal somite is produced in front on each side at the 

 junction of the tergum with the ])leuron into a short, stout, 

 bifid, and incurved process, which forms the abdominal ele- 

 ment of the thoraclco-abdomlnal hinge, and is received into 

 the groove in the hinder margin of the side of the carapace 

 already described. The pleura of the second abdomiiuil 

 somite are much more expanded in the female than in the 

 male. Ulie telson is elongate-triangular or obclavate in out- 

 line, its margin being at first rountled ami then ta[)ering In 



