Boone, Crustacea, Cruise of "Alva," 1931 29 



frontal width is only a little over half as wide as the proximal width. 

 The frontal margin is truncate at the base of the rostrum and on either 

 side is concave, the anterolateral angle being an acute spine. The 

 postlateral angles are rounded, the posterior margin slightly concave. 

 The median carina is bifurcate anteriorly for a short distance and is 

 also slightly bifurcate posteriorly for a short distance from the cervi- 

 cal groove to almost the posterior margin where it unites in a small 

 tubercle and terminates behind this in a small median spine, which in 

 old adults is sometimes blunt, nearly obsolete. There are two longi- 

 tudinal sulci, one on either side of the median carina and between each 

 lateral sulcus and the lateral margin there are three carinae on each 

 side, one about midway between the frontal margin and the cervical 

 groove but not extending to either ; outside this is a longer, somewhat 

 sinuate longitudinal carina that curves inward from the anterolateral 

 spine and runs backward to the posterior margin. The third carina, 

 which is the strongest of the series, is short, extending from the cervi- 

 cal groove obliquely backward to the posterior margin. The "cervi- 

 cal" groove is sharply defined. The third thoracic segment is short, 

 with the anterolateral angle produced to a sharp, procurved, acumi- 

 nate spine, the postlateral angle is a smaller, outcurved, triangulate 

 tooth ; the fourth segment is one and one-half times as long as the first 

 and has a sharp, procurved, outjutting anterolateral tooth which is 

 only two-thirds as long as that of the preceding segment; the post- 

 lateral angle is triangulate, directed outward. The fifth thoracic 

 segment is a little longer than the preceding segment, has its antero- 

 lateral angle a short, triangulate spine directed outward and its 

 postlateral angle a longer bluntly triangulate angle, with its hinder 

 lateral margin rounded; the sixth segment is about as much longer 

 than the fifth as the fifth is than the fourth and has its anterolateral 

 angle a stouter triangle than that of the preceding segment and the 

 postlateral margin rounded and concealed beneath the overlapping 

 flap that protrudes from the first five abdominal segments are subequal 

 in length and have the lateral margins similarly truncate, carinate and 

 terminating at the postlateral angle in a small acute spine. The first 

 abdominal segment has the characteristic stomatopod rounded flap at 

 the anterolateral angle, projecting over the base of the last thoracic 

 leg ; behind this flap on either side there is a short, transverse carina. 

 The sixth abdominal segment is a little shorter than the fifth and 

 not quite so wide, its lateral margin oblique above the base of the 

 uropoda. In addition to the carinate, lateral margins there are three 



