256 Capt. A. C. ^lacGilchrist on Decapod Crustacea 



prominent, projecting about as far as the salient edges of 

 tlie afl'crent branchial canal. 



The carapace of this si)ccies is globular, rhomboid al, not 

 very much broader tlian long, produced at the junction of 

 the antero-lateral and postero-lateral borders into a stout 

 horn-like process, which projects straight outwards, tapering 

 steadily but very gradually until in its distal fifth it rapidly 

 tapers off to a point ; the proximal end of the lateral pro- 

 cesses is not inflated or sausage-shaped, as in Ixa. Except 

 for a deep sulcus on cither side of the intestinal region, 

 separating it from the branchial regions, there is no pro- 

 nounced grooving of th.e carapace ; in the adult faint indica- 

 tions of grooving can be made out, and in the young this 

 grooving, although faint, is more discernible ; much more 

 distinct grooving can be seen in species of Arcania. The 

 carapace in the young is covered with small vesiculous 

 granules, which in the adult for the most part disappear, 

 except in the anterior part of the carapace and at the bases 

 of the processes. Between these vesiculous granules the 

 surface is rough and finely granular. At either end of the 

 posterior margin is a large, stout, papilliform process abovit 

 a third of the length of the lateral processes. On the middle 

 of the intestinal region there is a much smaller bullous 

 projection. The front is bilobed and projects further forward 

 than in Ixa. A very small bullous projection occurs on the 

 summit of the antero-lateral convexity of the subhepatic 

 region. 



The orbits are emarginate on the dorso-lateral aspect in 

 the region of the orhital sutures. The antennules do not 

 fold so obliquely (by reason of the front of the carapace 

 projecting more forwards) as in Lxa. The antennal peduncles 

 are small but distinct, and their flagella rudimentary. 



The external maxillipcds, as in Ixa, are partly sunken 

 below the level of the edges of the buccal cavern, which is 

 triangular, and the ischium is grooved along its inner border, 

 but the merus is quite different and peculiar in its shape. 

 The merus is grooved only in its basal fifth or so ; beyond 

 this its outer edge is bevelled to such a degree that the upper 

 surface in its distal two thirds is a mere ridge, and the 

 bevelled outer edge dovetails with the margin of the efferent 

 branchial canal and forms the inner wall of the afferent 

 branchial channel. The inner borders of the exognaths are 

 concave, their distal ends curving inwards and converging. 

 The surface of the exognath is strongly convex and, like the 

 raised outer border of the ischium, has a band of vesiculous 

 granules ; its distal free margin is well fringed with hairs 



