MUSEUM OF COMPARATIVE ZOOLOGY. 53 



ber, obtuse, and punctate. The marginal spines of the epimera of the second to 

 the fifth somite are all short, dentiform, and the posterior spine of the fifth 

 epimeron is merely represented by an obtuse angle. The lateral spines of the 

 sixth somite are about as prominent and fully as stout as in R. sculpta. 



The telson is longer than the carapax along the median line, exclusive of the 

 rostrum, and has nearly the same form and sculpturing as in R. sculj^ta, though 

 the tip is slightly more upturned. The outer lamella of the uropod is only 

 about two thirds as long as the telson, fully a third as broad as long, with the 

 lateral spine farther from the tip than in the other species and the margin 

 between the spine and the tip obliquely truncated rather than rounded. The 

 inner lamella is narrow and considerably longer than the outer. 



The specimen on which the above description is based is not carrying eggs, 

 and the genital orifices at the bases of the third pair of thoracic legs are not 

 easily discoverable ; but the appendages of the first and second somites of the 

 abdomen are like those of R. sculpta, and leave no doubt in regard to the sex. 



Length from tip of rostrum to tip of telson 54.0 ram. 



" of carapax including rostrum 23.0 



" of rostrum 12.3 



Breadth of carapax in front, including spines .... 8.7 



" " at cervical suture 7.0 



" " in middle 8.5 



Length of antennal scale 4.9 



Breadth of antennal scale 3.0 



Diameter of eye 2.5 



Length of telson 11.0 



Station 330, N. Lat. 31° 41', W. Long. 74° 35', 1047 fathoms. 



From Station 315, N. Lat. 32° 18' 20", W. Long. 78° 43', 252 fathoms, there 

 Ls a single small and imperfect specimen, evidently the young of this species. 

 This specimen is about 25 mm. long and differs from the one above described 

 in having the carinse of the carapax a little sharper ; the lateral carina of the 

 antennal region interrupted in the middle ; the marginal teeth of the abdom- 

 inal epimera smaller in proportion and the posterior tooth of the fifth epimeron 

 wholly wanting, leaving it bidentate like the third and fourth ; and the right 

 and left carpi in the second pair of thoracic legs of about eighteen and fifteen 

 segments respectively. 



