612 THE VOYAGE OF H.M.S. CHALLENGER. 



The body of the animal is anteriorly robust and continues so to the extremity of the 

 third somite of the pleon, behind which it suddenly narrows and becomes smaller. 



The carapace is nearly as deep as its length from the orbital to the postero-dorsal 

 margin, and is dorsally carinated from near the posterior margin, where the elevation is 

 broad, but anteriorly it gradually narrows to the apex of the rostrum. The rostrum is 

 about two-thirds the length of the carapace, and is armed with six small, subequal teeth, 

 the posterior of which stands upon the gastric region, and the others are subequally 

 distant from each other and from the sharp apical extremity. The under surface is 

 slightly dilated anteriorly and armed with three small, anteriorly directed, sharp teeth. 

 A strong ridge runs from the apex of the rostrum to the orbital margin, and above the 

 orbit there is a well-defined tooth from which an elevation passes back, traceable to the 

 pyloric region. The orbit is defined at the outer canthus by a sharp angle, the margin 

 then proceeds directly outwards and is armed with a well-formed antennal tooth, and then 

 passes down perpendicularly to the fronto-lateral angle, which is defined by a small sharp 

 tooth. 



The pleon is anteriorly as broad and deep as the carapace. The first somite has the 

 anterior division distinctly defined, the posterior being dorsally short, laterally broad, 

 and overlapping the postero-lateral margin of the carapace. The second somite has the 

 anterior division well defined from the posterior. The third somite is posteriorly 

 compressed, dorsally arcuate, and posteriorly produced in the median line ; the three 

 following somites become somewhat suddenly narrower, and continue tapering posteriorly 

 to the extremity of the telson. 



The oj)hthalmopoda are large and pear-shaped, the ophthalmus being broad and 

 carrying a small round ocellus, situated in contact with its posterior margin. 



The first pair of antennse has the peduncle subequal in length with the rostrum ; the 

 first joint is excavate on the upper surface for the reception of the eye, armed on the 

 outer side with a sharp stylocerite, and has the extremity furnished with two short 

 sharp teeth, one on the outer, the other on the upper surface ; the next two joints are 

 short and cylindrical, the distal being the smaller, and both are armed with a sharp tooth 

 on the upper distal surface. The flagella at the extremity are short and unequal, the 

 upper being the stouter and reaching but little beyond the extremity of the rostrum. 



The second pair of antennas carries a scaphocerite that is nearly as long as the first 

 pair of antennae, and a long flagellum that is broken off in the type specimen. 



The mandibles (fig. Id) have a cylindrical molar process, a flattened psalistoma, and 

 a two-jointed synaphipod. 



The first and second (fig. If) pairs of siagnopoda are unlike those of Spirontocaris. 



The third pair carries a large, bilobed mastigobranchia and a broad basecphysial plate 

 of extreme tenuity, from the inner surface of which there springs a filiform extension. 

 The base of the joint is broadly expanded on the inner ridge, the margin of which is 



