36 THE VOYAGE OF H.M.S. CHALLENGER. 



spines. Eostrum strong, of about the same leugtli as the carapace, distinctly denticulate. 

 Supra-orbital spines obsolete, antennal and branchiostegal spines well defined, the latter 

 remarkal:)Iy strong and finely serrate, pointing outward. Caudal segments sculptured 

 with transverse impressions, epimera produced into two acuminate lappets of nearly equal 

 size. Eyes pyriform, cornea rathi'r expanded. Antennal scale very small, ovate, outer 

 margin slightly serrate, apex oliliquely truncate, inner margin arcuate. Telson large, 

 with the terminal spines crescent-shaped and denticulate along the upper face. Uropoda 

 much shorter than telson. Length of largest specimen (which had probably reached its 

 maximum size) 98 mm. 



Remarks. — This form has been preliminarily recorded by the late Dr. v. Willemoes- 

 Suhm, in his manuscript notes, as a variety of Gnathophausia gigas. It should, 

 however, be certainly regarded as a distinct species, though closely related to the two 

 preceding ones. From Gnathojihansia gigas it may, among other characteristics, 

 be readdy distinguished by the unusually firm integuments, the distinctly marked dorsal 

 spine, and the remarkably long spines issuing from the iufero-posterior corners of the 

 carapace, a character which has given rise to the specific denomination " calcarata." 

 Futhermore, the rostrum is much coarser in structure, and the branchiostegal spines 

 considerably more developed ; while, as a final distinction, the eyes and the antennal scale 

 are of a somewhat different form. 



Description. — Of this handsome species there are two well preserved specimens in the 

 collection, both males. The largest specimen has a length of 98 mm.; the other is rather 

 smaller in size, the length being only 68 mm. These two specimens exhibit, it would 

 seem, some difference as regards the length of the rostrum and the lateral spines of the 

 carajsace, but in all other respects agree perfectly with each other. 



The general form of the body (see figs. 1, 2) closely approximates to that of 

 Gnathophausia gigas, though perhaps a trifle more robust. 



The integuments are throughout very much firmer than in either of the two preceding 

 species, and ajaparently they are somewhat indurated, giving to all the parts of the body 

 a more solid and distinctly defined appearance. 



The cai-apace, although rather large, does not cover the trunk to the same extent as 

 in the two preceding species, the last segment being partly exposed behind the posterior 

 margin. Both the lateral keels are strongly prominent, whereas the dorsal keel, as in 

 the former species, is distinct in the anterior ;iiid p(istei-ior parts only, being quite obsolete 

 in the middle of the carapace. The dorsal spine, projecting from the middle of the 

 posterior margin, is well marked, though not attaining any considerable length. On the 

 other hand, the spines projecting from the infcro-posterior corners of the carapace are 

 remarkably elongate and slender, mucroniform, and somewhat diverging, being finely 

 serrate at the edges. In the smaller specimen (see fig. 3) these spines are much produced, 

 reaching even to the end of the third caudal segment ; in the larger one (figs. 1, 2) they 



