62 



end of the rostrum are only four in number, in the other specimens five, like in the type 

 species from the West-Indies, excèpting one ova-bearing female from Stat. 262 and one male 

 from Stat. 314, in which six teeth are observed; these teeth are rather small and as a general 

 rule they gradually and regularly increase in size from the first to the last, sometimes, however, 

 like in an adult female from Stat. 262, two or three in the middle are equal and in the adult 

 male the 4 th tooth is even a little longer than the three preceding that gradually increase in 

 size, taken together, but here the 5 th or the 5 th and the 6 th are apparently not developed. The 

 shape of the rostrum, the form and the size of the spine on the lower margin and its position 

 with regard to the distal extremity of the antennal scale are typical, as figured in the "Recueil", 

 excèpting only that part of the rostrum which is situated in front of that spine. In Fig. 1 of 

 the "Recueil" the lower border between the spine and the apex of the rostrum appears namely 

 slightly convex, in all our specimens, however, quite straight, except the male, long 135 mm., 

 from Stat. 314, in which the rostrum is distinctly longer than the carapace : in this specimen in 

 front of the spine the lower margin appears very slightly concave, the upper margin 

 slightly convex, almost as much as in Bate's figure 2, Plate CXXV of the Report on the 

 Challenger Macrura, the rostrum appears, however, somewhat longer than in that figure and 

 the spine on the lower margin much smaller. Bate's figure of Acanth. armata is, however, 

 probably inaccurate, also as regards the spines of the abdominal terga, for the dactyli of the 

 5 ,h pair of legs are figured just as long as those of the 3"- 1 and 4" 1 pair. 



The rostral carina passes about on the middle of the gastric region gradually into a 

 low rounded ridge that may be continued to near the posterior margin of the carapace. At 

 about one-third the length of the carapace from its posterior border one observes, on either 

 side of the median ridge, a fine, shallow furrow, a tracé of the cervical groove; this groove 

 reaches downward only to midway between the dorsal ridge and the longitudinal ridge that 

 delimits the branchial region above-, in the adult female from Stat. 87 it extends upwards to 

 the dorsal ridge, curving slightly backward, but usually it does not reach the median ridge. 

 In the old female from Stat. 87 the dorsal surface between the cervical groove and the posterior 

 margin appears somewhat transversely rugose, presenting several irregulaf transverse furrows 

 or grooves, traces of which occur also in other specimens, while in the rest the dorsal surface 

 appears quite smooth. Orbital angle blunt, post-antennular spine small, post-antennal spine twice 

 as large, not buttressed by a long sharp carina reach ing backward to the 

 end of the hepatic groove, as occurs in Wood-Mason's variety fimbr ia ta. 



The spine of the 3 rd tergum is the largest of the four, that of the 4 lh is somewhat 

 shorter, measuring three-fifths that of the 3 ,d , the spine of the 5 th is the smallest of all, only 

 one-third that of the 5 th , while the spine of the 6 th tergum appears as long as that of the 4" 1 : 

 they are very well figured in the "Recueil". These spines, however, are described and figured 

 by Spence Bate as subequal and in his figure those of the 4"', 5 th and 6 th somite appear larger 

 than in our specimens : they are, no doubt, figured inaccurately, for the author has had the 

 opportunity of examining the type specimen(s) of Milne-Edwards himself. Sixth somite one- 

 third longer than fifth. Telson (Fig. 13, 13^) one and a half as long as the 6 th somite, terminating 

 in an acute spine; on either side of the latter three other spines are observed, of which the 



