Boone, Crustacea, Cruise of "Alva," 1931 181 



frontal portion is produced to a very broad, median triangulation 

 that tapers distally between the orbits into a laterally compressed, 

 non-dentate, distally acute rostrum, which extends as far forward 

 as the distal margin of the second peduncular article of the an- 

 tennule. Proximally the rostrum is defined on either side by a deep 

 sulcus that extends as far back as does the rostrum, approximately 

 at a point opposite the base of the eyestalk; there is no supra- 

 orbital spine, but the lateral margin of the rostral triangle, out- 

 side of the rostral sulcus is bent obliquely upward, forming the 

 inner lateral orbital margin. There is a decisive concavity of 

 the hinder orbital margin and outside of this a wide sublunate 

 depression on the carapace. The infraorbital tooth is blunt, nearly 

 right-angled, closely appressed, and has running from the apex on 

 the outer side a carina. Beyond this there is a strong antennal 

 spine, which is continued posteriorly as a strong carina, ridge- 

 like, defining the outer lateral margin of the suborbital concavity. 

 Below this carina the lateral wall is convex, closely appressed to 

 the body, the anterolateral angle acute, but scarcely spinose. The 

 abdominal terga are smooth, the first and second segments quite 

 wide, the third and fourth segments abruptly narrower; the re- 

 maining segments somewhat broken, but having the pattern shown 

 in Plate 49. 



The eye has a thick cylindrical stalk, two-thirds as wide as 

 long, shorter than the rostrum; the cornea is large, terminal, 

 hemispherical, extending not so far as the rostrum by about 

 1.5 millimeters. 



The antennulae have the peduncle only half so long as the 

 scaphocerite, or exceeding the rostrum by the length of the distal 

 article; the outer flagellum is substantially the thicker for the 

 proximal six rings, which extend to the tip of the scaphocerite, 

 and beyond this there are eighteen to twenty smaller, slenderer 

 rings, extending beyond the scaphocerite for a distance equal to 

 three-fifths of the length. The inner, slenderer branch is almost 

 as long as the outer one. 



The antennae have the basal article short and wide with an 

 acute spine at the outer distal angle, this spine being in line with 

 the antennal spine ; the scaphocerite is twice as long as the anten- 

 nular peduncle, subovate, with the outer lateral margin nearly 

 straight, terminating in a very acute, subdistal spine, the distal 

 margin is quite broadly and somewhat unevenly rounded, crenu- 



