Boone, Crustacea, Cruise of "Alva," 1931 83 



its anterolateral margins widely rounded, its exposed ventral face 

 concave, this concavity increasing posteriorly. The bases of the 

 third pair of legs are produced into elbow-like nodes at their ex- 

 posed inner ventral angles. 



The male petasma arises from the inner lateral face of the pe- 

 duncle of the first pair of pleopoda and these plates fuse to form the 

 curiously shaped, tubular organ shown in fig. 4; the distal end 

 of each half is divided into a subdistal, lateral, horn-like, conical 

 process, with a linear aperture on its distal-lateral side; immedi- 

 ately above this process and bent over it is the larger distal pro- 

 cess, mouse-ear shape, which arises from the inner distal angle 

 of the main process and forms a hood-like, externally convex, in- 

 ternally concave, upper aperture to the tubular main portion of 

 the petasma. Between the bases of the fifth pair of legs is a trans- 

 verse ridge posteriorly and anterior to this the surface is de- 

 pressed in the median region, with a pair of small, submedian 

 nodes anteriorly. Between the bases of the fourth pair of legs 

 there is a small median plate with the exposed surface depressed 

 and the anterolateral margin rounded. 



The eye is short-stalked, the cornea reniform, well protected. 



The antennulae have the basal peduncular article laminate be- 

 neath the cornea and somewhat concave, with a lobate-acuminate 

 process arising from its inner proximal angle and forming the 

 inner lateral wall of the corneal cavity; the second article is 

 three-fourths as long as the first article ; the third article is short, 

 extending as far as does the scaphocerite ; the flagella are nearly 

 subequal in length, each branch is about as long as the outer lateral 

 margin of the scaphocerite. 



The antennae have a scaphocerite which is quite wide proxi- 

 mally, but much narrowed distally, the inner lateral margin taper- 

 ing, while the outer lateral margin is relatively straight, termi- 

 nating in a subdistal tooth, the apical margin is rounded ; the sec- 

 ond and third articles are cylindrical ; the flagellum is very fine, 

 about one and one-half times the length of the carapace. 



The external maxillipeds extend to almost midway of the 

 scaphocerite. 



The first pair of legs extend to midway of the carpal joint of 

 the external maxillipeds, while the third pair of legs exceed the 

 maxillipeds by about the length of the related fingers. The first 

 pair of legs differ from the others in having the ischial and meral 



