I. '21. * 57 



and a pair of smaller spines near the base. Between or slightly 

 in advance of the latter there are one, less commonly two, 

 small or medium-sized unpaired spines. On the under sur- 

 face near the l)ase there is a single large curved spine, projecting 

 betw^een the eyes. ^ 



The regions of the carapace are well-marked. The gastric 

 area is large and arched and is separated by the cervical groove 

 from the similarly arched anterior part of the cardiac area. 

 The linea anomurica is distinct. The dorsal surface Of the 

 carapace bears a large number of strong spines, which spring 

 from broad bases and taper rapidly to sharp points. The 

 posterior margin is straight, slightly arched in the middle. It 

 is bordered by a row of spines Avhich are as large as or larger 

 than those on the dorsal surface. The spines are continued 

 along the lateral margins and increase in size from behind 

 forwards. They reach their greatest development on the antero- 

 lateral edges, where four or five are frequently very large, and 

 end in a medium-sized spine limiting the outer angle of the 

 orbital notch. 



The second abdominal segment is fused to the first and 

 consists of one piece, not of three or five, as in some nearly 

 allied species. These segments together form a solid strongly 

 calcified plate, which, in the natural position, is practically 

 vertical, lying in a plane at right angles to the dorsal surface 

 of the carapace and to the posterior segments of the abdomen. 

 The plate bears a number of spines which are roughly arranged 

 in three rows. In the first row there are only two spines lying 

 in the centre. The second and third rows mark the positions 

 of the first and second abdominal segments and in these the 

 spines tend to be largest in the middle. 



The remaining part of the abdomen is pressed closely against 

 the very broad sternum, as in the Brachyura. The third, fourth 

 and fifth segments are each represented by a pair of plates, 

 roughly oval in shape, which slope outwards and towards the 

 telson. The plates do not meet in the centre, but are separated 

 by a triangular area of soft skin, thickly studded with round 

 calcified tubercles. Outside the large paired plates of the 

 third, fourth and fifth segments there is on eacJh side in the 

 male (in the female only on the right side) a row of small 

 marginal plates. These and also the large plates bear numerous 

 broad-based spines. The sixth segment is represented by a 

 single central plate of about the same size as the lateralones 

 of the three preceding segments. Beyond it is the short rounded 

 telson. 



In the female the posterior part of the abdomen is markedly 

 asymmetrical; The plates of the third, fourth and fifth seg- 

 ments are much larger on the left than on the right and, as 

 stated above, the row of small marginal plates is absent on the 

 left. 



1 Bouvier (1898) refers to this spine as " le rostre " and calls the rest of the 

 structure " la sailiie dorsalo du rostre." 



