16 G. 0. Sais. 



named' the different proportion between the carapace and the 

 exposed part of the body, the number of caudal segments, 

 and the sculpturing of the carapace, which latter character 

 has given rise to the specific name here proposed. 



Description. 



The chief dimensions of the specimen are as follows: — 

 Total length from the frontal margin to the end of the last 



caudal segment 42 mm. 



Median length of carapace 22 — 



Greatest width of same 19 — . 



Length of exposed part of body 20 — 



Length of caudal part 8 — 



Length of caudal filaments 30 — 



. The present specimen differs from the female of A. 

 numidicus not only in its large size, but also in the general 

 form of the body (see fig. 1). Thish is on the whole much 

 more robust, the carapace being considerably larger in pro- 

 portion to the exposed part of the body. As to form, the 

 carapace is moderately vaulted, and, seen dorsally, regularly 

 oval in outline, with the greatest width not nearly attaining 

 the median length. The frontal margin is broadly rounded 

 and together with the side-edges forms a quite even and 

 uninterrupted curve as far as the tips of the terminal lobes. 

 The latter are obtusely acuminate and scarcely appressed 

 to the body, and the posterior sinus appears rather wide 

 and evenly rounded at the bottom. The marginal denticles 

 of this sinus are very distinct, about 15 on each side, and, 

 on a closer inspection, the adjacent part of the lateral edges 

 is also found to be finely denticulate for some distance. 

 The cervical sulcus and dorsal keel are very strongly marked; 



