Boone, Crustacea, Cruise of "Alva," 1931 151 



Technical description: Carapace, including the rostrum, 

 five-sixths as long as the abdomen, including the telson. The ros- 

 trum, measured from the orbital angle to the tip, equals one-half 

 or slightly more than one-half of the length of the carapace. The 

 carapace is laterally compressed, rounded above, the distal two- 

 fifths produced to a crest which is continuous with the rostrum ; 

 the rostrum is blade-like, directed forward, slightly downward, 

 with the tip slightly upward directed, Tlie superior margin of the 

 crest is cut into one acute, procurved tooth on the gastric region 

 at the origin of the crest on the rostrum and followed usually by 

 seven (sometimes eight, rarely six) similar teeth, well spaced; 

 the eighth tooth sometimes being well back from the acute tip and 

 sometimes very close to it. Anterior to each tooth on the margin 

 of the rostrum is a fine brush of cilia. On the inferior margin of 

 the rostrum there are usually three teeth (sometimes two, rarely 

 four), the proximal one being about opposite the base of the sec- 

 ond peduncular joint and the distal one opposite the next two 

 distal teeth of the upper series. The superior orbital margin is 

 lightly carinate and this carina continues forward on the lateral 

 surface of the rostrum, vanishing near the tip. The outer orbital 

 canthus is rounded and the anterolateral angle is also rounded 

 and unarmed. There is a short, acute, hepatic spine, and slightly 

 above it a short carina that runs obliquely forward and upward, 

 terminating in an acute spine, just below and distinct from the 

 rounded optic canthus. Below and posterior to the hepatic spine 

 there is a distinct short sulcus extending backward obliquely. The 

 abdomen is compact, dorsally rounded and unarmed. The epimera 

 of the first segment are bluntly rounded, those of the second seg- 

 ment are widely rounded, expanded, overlapping those of the 

 two adjacent segments ; the epimera of the third segment are nar- 

 row, bluntly rounded ; the epimera of the fourth, fifth and sixth 

 segments are truncated, with the postlateral angles increasing- 

 ly acute. The fourth and fifth segments are slightly incised on 

 each side posteriorly in the median lateral region ; the sixth seg- 

 ment is produced in this region into an acute small triangle that 

 projects above the outer lateral portion of the telson. The telson 

 is one and two-thirds times as long as the sixth segment, rounded 

 on the upper surface, narrowed distally, the distal margin tri- 

 angulate, armed on either side with an inner pair of large triangu- 

 late, articulate spines extending somewhat beyond the tip of the 



