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



hepatic ridge, where it terminates somewhat abruptly, corresponding almost completely 

 with the length of the branchial region. Inferiorly, or below the antennal carina, is 

 another that commences almost in connection with it, close to the posterior margin, 

 following the curve of the posterolateral margin of the carapace and then running parallel 

 with the antennal carina, and dying out just before reaching the anterior margin. 

 Another carina, the fifth on the same side, commences in the posterior margin, con- 

 fluent with the antennal carina, and follows a line within, but subparallel to, the inferior 

 margin of the carapace. These several carinas, eleven in all including the dorsal, are 

 more or less constant in the several species, and form a peculiar feature in the genus. 



The first somite of the pleon has the anterior division strongly defined from the 

 posterior, the dorsal surface of which is elevated, slightly carinated, and the posterior 

 margin deeply notched in the median line. The lateral or coxal plates are very large and 

 deep, the anterior being deeper in this species than in most others, and are broader at 

 the inferior margin than at the dorsal surface of the somite. The infero-anterior angle 

 projects forwards, and the anterior margin overlaps the sides of the carapace, the dorsal 

 portion of which falls into the deep depression formed between the anterior and posterior 

 division of the first somite of the pleon. The third and following somites have the two 

 divisions confluent ; the dorsal median line is carinated and the posterior margin is pro- 

 duced to a sharp-pointed tooth in all except the first two, which are regularly notched, 

 the second somite not being quite so strongly excavate as the first. 



The telson is dorsally grooved and laterally compressed, the margins being smooth 

 and unarmed. 



The whole surface of the animal is covered with small irregular corrugations, which, 

 so far as I have observed, is a feature peculiar to this genus. 



The ophthalmopoda stand near the margin of the carapace at the extremities of the 

 ophthalmic somite, and are consequently placed widely apart at their base ; they are pyri- 

 form and furnished on the inner side halfway between the articulation and the ophthalmus 

 with a small bead-like tubercle. The ophthalmus is black and the margin even, except 

 on the posterior side, where a small excavation exists producing a prominent point some- 

 what like an ocellus, but not structurally separate from the ophthalmus. 



The first pair of antennas has the first joint excavate to receive the eyes, and carries a 

 sharp-pointed stylocerite ; the two succeeding joints are short, and the last supports two 

 unequal flagella that are longer than the carapace. 



The second pair of antennae carries a scaphocerite that reaches a little beyond the 

 rostrum, terminates in a rounded apex, and is furnished on the external margin with a 

 sharp tooth. The tooth on the under surface of the second joint is short and pointed. 



The oral appendages offer nothing characteristically distinct from those of other species. 



The second pair of gnathopoda is tomentose, as are, to a slight degree, all the 

 appendages of the pereion. It appears to consist of only five joints, the ischium and 



