30 



of the carapace. These margmal spines are arranged as follows : 

 in the front part there are six which are sharp and slightly 

 curved forwards ; in the centre there are three very small, and 

 in the hind part seven large spines, these latter thicker and 

 blunter than the others ; they increase in size posteriorly. Along 

 the median dorsal line there runs a series of prominent spines 

 arranged thus : — 



Rostrum + 1, 2, 1, 1,; 2, 2, 1, 2, 

 (The semicolon denotes the position of the cervical groove.) 



Between this median carina and the lateral margin on the 

 posterior half of the carapace there is a row of six spines, the 

 branchial carina, decreasing slightly in size anterioity. These 

 run parallel to the margin and are nearer it than to the median 

 carina ; they extend from the hind margin to the cervical 

 groove. There is a large single spine at the point of bifurcation 

 of the cervical groove, one immediately in front of this, and also 

 one external to it. Of the submarginal carinae the upper is 

 minutely denticulate in its anterior third, and fades away 

 behind this ; while the lower and shorter one is formed of eight 

 or nine spines, the last three of which are small, but the others 

 large and prominent. Between the orbital sinus and the lower 

 part of the cervical groove there is a curved row of three or four 

 very small spines. 



The abdomen is shorter than the carapace and very much 

 narrower ; it tapers slightly posteriorly. Each segment bears 

 one or m^ore large median dorsal spines arranged thus :1,3, 3, 

 3, 3, 1, 1, the last on the basal part of the telson. In the triple 

 spines of the central segments the mJddle point is the largest 

 and the front one is usually less erect than the others, sometimes 

 almost horizontal. Besides these the abdominal segments bear 

 other spines. On the sixth segment there is one at each edge 

 of the tergum, and one projecting backwards horizontally from 

 each postero-lateral angle. On the second, third, fourth, and 

 fifth segments there is a spine at each edge of the tergum and 

 also one on the middle of each pleuron. The pleura of the first 

 segment are narrow and tapering. At each side of this segmient 

 there is a lateral extension which is buckled firmly to the hind 

 part of the carapace. The second pleura are broad and expanded, 

 with six or seven small spines on the lower margin. The pleura 

 of the next three segments are all narrower than those of the 

 second, and have each four or five marginal spines. The sixth 

 pleura end in a single sharp point. They all bear setae at least 

 on their posted o:r margin. 



The telson is long and tapering, and has small spines on either 

 margin and on two ridges running along the dorsal surface, 

 besides the single large spine already mentioned. Its tip is pro- 

 longed into a sharp needle-like point. 



The eyestalks are fixed and immovable in the orbital sinuses. 

 Each bears in front a blunt conical process. 



