770 THE VOYAGE OF H.M.S. CHALLENGEE. 



depth, 175 fathoms ; bottom, blue mud. Nine specimens ; seven females, two males. 

 Trawled. 



Station 310, January 10, 1876; lat. 51° 27' 30" S., long. 74° 3' 0" W.; Sarmiento 

 Channel ; depth, 400 fathoms ; bottom, blue mud ; bottom temperature, 46°*5. Six 

 specimens ; three males, three females. Trawled. 



Station 311, January 11, 1876; lat. 52° 45' 30" S., long. 73° 46' 0" W.; off Port 

 Churruca ; depth, 245 fathoms ; bottom, blue mud ; bottom temperature, 46°. Four 

 specimens ; one female, three males. Trawled. 



The carapace is dorsally carinated in the median line from the post-cardiac region to 

 the anterior extremity, which is produced to a laterally compressed rostrum that is rather 

 longer than the carapace, and armed above with four or sometimes five large teeth, two 

 of which are posterior to the frontal margin and the others placed widely apart on the 

 rostrum ; the under margin is suddenly deeply produced and armed with three strong 

 teeth. The rest of the carapace is smooth and j)olished, excepting for two short carinae 

 on each side, the upper of which commences at the frontal margin in the first antennal 

 tooth and loses itself in the carapace, gradually lessening in intensity towards the 

 posterior extremity ; the second commences in the second antennal tooth, which stands 

 just within the frontal margin, and loses itself just behind the hepatic region. 



The posterior margin of the carapace is laterally overlapped by the anterior margins 

 of the coxal plates of the first somite of the pleon. 



The plastron or ventral surface of the pereion is triangular, rather broader at the 

 posterior portion in the females than in the males. The two somites that carry the 

 gnathopoda are so narrow that the appendages are almost in contact, but on the next 

 somite, or that which carries the first pair of pereiopoda, there arises from the posterior 

 margin on each side of the median line a long, sharp, and slender tooth, which from the 

 base curves downwards and obliquely forwards (fig. 2). 



On the next somite, or that which supports the second pair of pereiopoda, a second 

 pair of teeth exists which are longer and broader at the base. On the next somite the 

 teeth are shorter and exist more in the form of broad and obliquely planted plates, 

 though in some specimens, especially from other stations, they are prolonged to flattened 

 sharp-pointed teeth. Similar plates exist, but less conspicuously developed, on the two 

 posterior somites, but in the specimens from Station 306a, which are males, they are both 

 prominent and pointed. 



The pleon is dorsally smooth, has no carina, and has the lateral plates large and deep. 

 The third somite is slightly arcuate and dorsally compressed in a manner suggestive of 

 an obsolete tubercle, such as exists in Gonatonotus ; the posterior margin is slightly 

 produced in the median line beyond the anterior margin of the following somite. The 

 three posterior somites are narrower than the preceding, the fourth somite like the preceding 



