REPORT ON THE AMPHIPODA. 979 



Branchial vesicles as in the preceding pair. First joint of the limb longer than in the 

 third perseopods, more convex in front, the hind margin long and nearly straight, with 

 few serrations, the lower margin more deeply overlapping the second joint ; the third 

 joint longer and larger than in the preceding pair, with spines at five points on the 

 straight serrate front margin, and at four of the hind margin, which is convex above and 

 straight below. 



Fifth Perseopods. — Side-plates deeper behind than in front, but not lobed. The 

 first joint like that of the fourth peraaopods, but less convex in front ; the fourth joint 

 shorter than the third, with four groups of spines on the straight serrate front margin, 

 and an apical group behind ; the fifth joint about as long as the third, with six groups of 

 spines along the serrate front margin ; the finger much curved, about half the length of 

 the fifth joint. 



Pleopods. — Coupling spines not examined ; cleft spines four in the series on the third 

 pair ; the joints of the rami on the same pair numbering eighteen. 



Uropods similar to those of Eusiroides pompeii ; telson comparatively shorter than 

 in that species, the apices simple, but as these have a worn appearance in the specimen, 

 this mark of distinction cannot be relied on ; the lateral margins are without the slight 

 sinuosity observable in the two preceding species ; in fig. ur.3, the telson being removed, 

 the acute apex of the ventral side of the sixth pleon-segment is seen. 



Length. — The specimen, in the position figured, measured, in a straight line from 

 the rostrum to the dorsal extremity of the third pleon-segment, about half an inch. 

 The specimen was dissected unfortunately before the line of measurement had been 

 drawn. 



Locality. — Station 320, off Monte Video, February 14, 1876; depth, 600 fathoms; 

 bottom, green sand ; bottom temperature, 37°'2. One specimen. 



Remark. — The specific name is derived from Crassus, the colleague of Caesar and 

 Pompey (or Pompeius) " in the first triumvirate " of Roman history. The name was chosen 

 with a view to calling attention to the close alliance between this and the two preceding 

 species. It may be convenient to compare the localities from which the three were respec- 

 tively obtained : Eusiroides csesaris came from Station 161, lat. 38° 22' 30" S., long. 144° 

 36' 30" R; Eusiroides pompeii horn. Station 151, lat. 52° 59' 30" S., long. 73° 33' 30" E.; 

 and Eusiroides crassi from Station 320, lat. 37° 17' S., long. 53° 52' W., so that, though 

 not very remote from one another as regards the latitude, in respect to longitude the 

 three species cover an enormous space. 



