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



the one on the hepatic region is considerably enlarged. The carina on the pleon, as 

 pointed out by Olivier, is " flattened on the summit and ridged at the margin " ; this is 

 caused by a cleft existing in the median line of the posterior margin, which admits of the 

 crest of the next somite being raised into it, and thus a more extensive vertical move- 

 ment is provided. This peculiar condition I have seen in other carinated species of 

 Crustacea, but to a less conspicuous extent. 



The postero-lateral margins of the coxal plates are strongly denticulated. The first 

 and second are only dentate at the apex ; the third is bidentate, the fourth and fifth are 

 tridentate, the posterior tooth being smallest. The sixth or posterior is bidentate, and 

 has also a tooth in the median dorsal line. The body generally is pilose, and the margins 

 of the pleonic somites are fringed with hairs. 



The ophthalmopoda are short, being about half the length of the rostrum. 



The first pair of antennas is short, having the first joint of the peduncle scarcely 

 longer than the rostrum ; it carries a small prosartema and a long stylocerite that 

 reaches nearly to a level with the distal extremity of the first joint, the outer angle of 

 which terminates in a strong tooth ; the second joint is short and cylindrical, and the 

 third is very short and carries two very small and slender flagella. 



The other appendages are very like those of the preceding species, except that the 

 second pair of gnathopoda is scarcely so long and is more robust. 



The ventral surface of the pereion is hirsute, especially marked on the coxal and 

 basisal joints of the pereiopoda. In our specimen the ventral plate or thelycum com- 

 mences between the ultimate pair of pereiopoda, and projects in the form of a sharp 

 styliform tooth as far forwards as the second pair of j>ereiopoda, a deep hollow existing 

 in the median line at the base ; between the anterior pairs of pereiopoda is a pair of 

 sharp spinedike teeth, and between every pair of pleopoda is a strong tooth-like 

 tubercle. 



This specimen was taken south of New Guinea. De Haan records his specimen from 

 Japan. Dr. Stimpson found his in 20 fathoms of water on a bottom of shells and sand 

 in the Gulf of Kagosima, and M. Peron brought the typical specimen, described by 

 M. Olivier, from " la mer des Indes." 



Sicyonia lasvis, n. sp. (PL XLIII. fig. 5). 



Surface of the animal smooth. 



Rostrum armed with five teeth above, and one below at the apex, and on the dorsal 

 crest with two in the median line, one on the gastric region and the other on the 

 cardiac, whence a small carina extends to the posterior margin of the carapace. Hepatic 

 tooth small. Pleon slightly carinated. First and second somites armed with an anteriorly 

 directed tooth ; posterior margin of each somite cleft in the dorsal median line, last somite 



