REPORT ON THE CRUSTACEA MACRTJRA. 155 



On the pleon the dorsal median teeth are very prominent, and continue to the 

 telson ; they are all anteriorly directed, and exhibit a tendency, which increases posteriorly, 

 to carry ;i second small tooth, which on the sixth somite breaks into a serrate arrange- 

 ment, and this is repeated on the telson, though to a less extent. 



The first pair of pereiopoda is long and slender, and has the meros armed with one, 

 two, or three sharp teeth on the outer margin, and one at its outer distal angle, and the 

 carpos armed with a sharp tooth on the outer margin, a little behind the propodal joint. 



The posterior pair of pereiopoda has the pollex in both sexes shorter than the 

 dactylos. 



Length — male, 46 mm. (l"8 in.) ; female, 50 mm. (2 in.). 



Habitat.— Station 305b, January 1, 1876; lat, 47° 48' S., long. 74° 46' W.; south- 

 western coast of South America; depth, 160 fathoms; bottom, blue mud. 



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

 Strait; depth, 245 fathoms; bottom, blue mud ; bottom temperature, 46°. Nine specimens. 



There was only a single specimen of this species, and that a male, taken at Station 

 305b, in the channel between the coast and the islands that lie upon the Pacific side of 

 Patagonia. But at Station 311, where the situation was very similar, though nearer the 

 Strait of Magellan by some three hundred miles, on a similar sea-bottom, and within 

 the same chain of littoral islands, there was a larger number taken, a circumstance that 

 has allowed me to examine in detail the structure of this species more minutely than in 

 most of the other forms, of which the specimens were fewer. 



The lateral margins are nearly parallel to each other, the denticulation is bolder than 

 usual and slightly curved upwards and forwards, and the anterior angles approaching a 

 little towards each other ; the surface is sprinkled with small denticles, and a row of 

 more important ones runs from the post-orbital angle posteriorly and inwardly. In some 

 specimens the anterior tooth is larger than either of the others, and at the opposite ex- 

 tremity they are connected on the outer side with a group of others ; on the ridge of 

 the cervical suture, half way between the median line and the lateral margin, is another 

 group of three or four small sharp teeth. Corresponding with the line of separation 

 between the branchial region and that of the internal viscera, is a curved row of small 

 teeth, commencing just behind the cervical fossa and running nearly parallel with the 

 lateral margin to the posterior extremity of the carapace. On the inner side, between 

 this row of denticles and the median ridge of the carapace, is a group of several other 

 teeth sparsely scattered about, and the entire surface is sprinkled with short hairs, the 

 longest of which are on the branchial region. Besides the rostral teeth there is one 

 situated on the anterior margin at the internal angle of the orbital notch. 



The somites of the pleon are all dorsally armed with strong anteriorly-directed teeth, 

 each carrying a more or less conspicuous denticle behind it, of which that on the third 



