Boone, Crustacea, Cruise of "Alva," 1931 23 



and on either side separated by a white ovate spot from the lateral 

 black lobe. 



Technical description: The carapace is glabrous, polished, de- 

 void of carinae, decidedly convex from side to side, the greatest width 

 nearly equal to the length, exclusive of rostrum, the anterior width 

 nearly equal to the posterior. The anterior margin is rounded, 

 slightly sinuate, with a faint, rounded, median point ; the lateral mar- 

 gins are rounded, with the anterolateral and posterolateral margins 

 very rounded, the posterior margin is deeply concave; the gastric 

 grooves are deep, extending almost the full length of the carapace; 

 the cervical grooves are not so well defined, being indicated by short, 

 curved depressions on either side and confluent with the gastric 

 grooves. 



The rostrum is cordiform, wider than long, this maximum width 

 occurring in advance of the proximal border; produced to a median 

 distal apex, which is very slightly deflected and thickened dorsally, 

 a median carina on the distal third of the rostrum. The lateral mar- 

 gins are widely rounded and very slightly concave, anteriorly con- 

 verging abruptly to the apex. 



The third thoracic segment is exposed dorsally, filling in the con- 

 cavity of the posterior margin of the carapace; the fourth thoracic 

 segment is also exposed dorsally and is only one-half as long as the 

 fifth segment which has its lateral margin transversely channelled by 

 a wide, shallow groove, that separates the blunted anterior and pos- 

 terior carinae, which converge toward the inferior region of the seg- 

 ment. The sixth and seventh segments are successively a trifle wider 

 and have their lateral margin rounded anteriorly and subrectangular 

 posteriorly ; the fifth segment with a curved carina transversely above 

 the margin, while the sixth segment has a recurved carina here. The 

 first to fifth abdominal segments inclusive have the lateral margins 

 concave, with the postlateral angles bluntly rounded; the sixth ab- 

 dominal segment has a thickened lateral margin, defined inwardly by 

 a curved longitudinal groove. On the inferior margin at the antero- 

 lateral angle is a small spine, directed posteriorly, over the base of the 

 uropod. On the second to fifth abdominal segments inclusive, there is 

 a short, definite longitudinal sulcus that divides the anterior portion 

 of each segment in three subequal regions; sometimes there is also 

 present a faint depression on either side of the median line, defining 

 a shallow elevation. 



