Boone, Crustacea, Cruise of "Alva," 1931 61 



the cornea is hemispherical, terminal, scarcely larger than the 

 stalk, with excellent visual range. 



The abdominal terga, one to six, inclusive, are elevated to a 

 median longitudinal carina, on the first segment being less ac- 

 centuated than those of the second, third and fourth segments, 

 which increase in strength in the order named, while that of the 

 fifth segment is posteriorly produced into an acute spine over- 

 hanging the sixth segment ; the latter has the anterior half of the 

 carina replaced by a faint sulcus beneath the spine, while on the 

 posterior half there are a pair of submedian, blunt tubercles, fol- 

 lowed on the posterior margin by a big, blunt tubercle that makes 

 a prominent peak on the posterior margin. Each segment has a 

 transverse depression across its anterior border, and also an arcu- 

 ate, transverse sulcus submedially. The remaining elevated por- 

 tion of the surface is ornamented by numerous, large, low, rounded 

 tubercles, which tend to form transverse lines of beads along the 

 margins and across the median zone of the respective segments. 

 The epimeral border of the first segment is terminated in a small, 

 acute, procurved tooth, that of the second, third, and fourth seg- 

 ments each in a downward, outward directed tooth, while the fifth 

 segment has two backward pointed, procurved teeth on each side, 

 separated by a concavity ; the inner tooth being opposite the outer 

 angle of the peduncle of uropod. The telson is as long as wide 

 with the distal margin broadly rounded, the proximal portion soft 

 but thicker than the more flexible distal portion. The uropoda is 

 similarly flexible, expanding laterally ; the peduncle is small with 

 an acute tooth above the base of the inner blade. Both blades have 

 each a pattern of longitudinal grooving with the addition on the 

 proximal area of a few flat, oblique carinae. 



The sternal plastron is of the shape figured (Plate 15, A), 

 the anterior end being greatly narrowed and bounded by a mod- 

 erately incised double tooth-like ridge and on either side the lat- 

 eral margin is similarly up-bent, rim-like, thickened and termi- 

 nating posteriorly on each segment in an acute tooth-like process. 

 In addition to this there are on the median ventral line of seg- 

 ments one to five, inclusive, an acute, ventrally directed tooth, 

 these increasing in size from the first to fifth segments. The first 

 five abdominal segments have each a transverse, narrow, calcare- 

 ous bar, which on segments one, two and three each has an acute 

 median spine, on either side of which there is a series of coarse 



