between the i^' and the 2"<^ and between the 4''' and the 5''' being the smallest of all. The 

 teeth are of equal size, excepting the s'*' that is a little smaller; a minute prominence occurs 

 at the base just behind the i*' tooth, only visible, like the teeth themselves, by means of a 

 magnifying glass. The horizontal terminal part of the upper margin is unarmed and reaches 

 to the middle of the 2""^ joint of the antennular peduncle. The lower margin of the rostrum 

 that forms a sort of hood over the eyestalks, recedes, regularly arched, backward and down- 

 ward and bears a very small denticle, somewhat nearer to the extremity of the rostrum than 

 to the anterior tooth of the upper margin ; this ventral tooth is still much smaller than the 

 t'*" tooth of the upper border. In the other somewhat larger specimen the tip of the ro.strum 

 is broken off, so that it hardly reaches as far as the p' joint of the antennular peduncle and 

 it remains uncertain whether the minute ventral tooth occurs also here; there are in this 

 specimen only 4 teeth on the upper margin, of which two are placed somewhat behind the 

 orbital sinus, the 3"^^ just over it and one and a half as far distant from the 2'"' tooth as from 

 the 4"'; immediately behind the 1="' tooth the same minute prominence as in the other specimen. 



Outer canthus of the rather deep orbital sinus rectangular, the orbital margin making 

 a right angle with the anterior border of the carapace, but a post-antennular spine, which is 

 obvious in Bate's figures of Acanth. Batei Faxon (Challenger Macrura, PI. CXXV'I, Fig. 6, 

 less distinctly also in Fig. 5), does not occur in Acanth. Sibogae. The anterior margin of the 

 carapace runs, from the outer orbital angle, at first for a .short distance straight downward but 

 soon it runs more obliquely, behind the antennal peduncle, and this oblique part of the margin 

 is slightly concave. Post-antennal spine well-developed, salient, a little remote from the margin 

 and flanked by a carina that runs at first backward and then curves downward to the hepatic 

 groove. Cervical groove quite conspicuous; it proceeds from the dorsal carina, which 

 it does not seem to intersect, obliquely downward and forward to near the antennal carina and 

 then curves forward, in a .semicircular curve, to meet another groove that commences at the 

 orbital margin and that runs obliquely backward and downward; this shallow orbital groove is 

 flanked by a low keel that gradually passes into the posterior ridge of the cervical groove. 

 Hepatic groove well defined, proceeding from the cervical groove, behind the semicircular curve, 

 at first oblicjuely downward and forward to near the antennal carina and continuing then, 

 buttressed by a keel, obliquely downward and backward to near the posterior extremity of the 

 antennal carina. From the angle thus formed a strong prominent ridge or crest, the 

 upper boundary of the branchial region, runs horizontally backward to near the posterior margin 

 of the carapace, at the level of the antennal carina and somewhat farther distant from the 

 dorsal carina of the carapace as from the lower border; from the posterior extremity of this 

 ridge a narrow groove runs obliquely forward and downward, gradually diverging from the 

 ridge, to near the hepatic groove. 



The abdomen almost fully resembles that of Acatith. Batei Faxon (Challenger Macrura, 

 PI. CXX\'l, Figs. 5, 6). The two first somites are rounded, the 3'''' is carinate, but the feeble 

 keel ends abruptly, there being no tooth at the posterior margin ; the three following somites 

 are sharply carinate and distinctly produced to a small tooth, the teeth are of equal .size and 

 the notch on the 4''' .somite is situated at the posterior third. Sixth .somite 2Yj-times as long 



I 



