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



situated near the base of the rostrum ; in the female they are of moderate size and 

 distant; in the male large and closely approximated. 



Habitat. — Off Port Jackson, Australia ; off Sibago Island and in other places amongst 

 the Philippine Islands, and in the Arafura Sea, September 13, 1874. 



Though Prof. Dana passes without notice the peculiar tail setae and remarkable 

 trifid beak of this species, many of the other characters figured and described by him as 

 pertaining to Pontellina acuta (as, for instance, the fifth foot of the male and the 

 twenty-one- and twenty -two-jointed antennas) are so peculiar and so exactly similar to 

 those of the specimens now under consideration, that it seems almost certain that the 

 species referred to in both cases are the same. The two lateral spines of the rostrum, 

 though large, may easily be overlooked in certain positions of the animal. Dana's 

 measurement, 1-1 0th of an inch, is much less than mine, but a similar discrepancy occurs 

 in many other cases. Dana's specimens, like ours, were obtained in the Eastern Seas : — 

 " East Indies, off the south-east end of Mindoro, and in the China Sea." It should be 

 noted that, owing to the position in which the animal is drawn, the eyes in fig. 1 do 

 not appear so far distant as they ought to do. 



2. Pontella detruncata, Dana (PL XXYI. figs. 8-15 ; PI. XLV. fig. 20). 



Pontellina detnencata, Dana, Crustacea, IT. S. Expl. Exped., p. 1143, pi. lxxx. fig. 7, a.-i. 



Length, l-8th of an inch (3 mm.). Head subtruncated and obscurely angular in 

 front, posterior angles of the cephalothorax rounded off or angular, not produced into 

 long spines ; rostrum furcate, of moderate length. Anterior antennae twenty-two- 

 jointed, densely clothed externally with long setae towards the base, and on the inner 

 aspect in the same region fringed with numerous delicate hairs (fig. 8) ; the right 

 anterior antenna of the male (figs. 9, 10, 11) is much swollen in the middle, and bears 

 three denticulated plates, the uppermost and lowest having produced, rounded, and 

 thickened extremities ; the denticulations of all three plates differ somewhat in character, 

 those of the upper plate being slender and recurved and graduated in length from the 

 middle to each extremity ; in the middle plate the teeth are straight and sharp, each set 

 upon a distinct, enlarged base, while those of the last plate are short, stout, and 

 triangular. Inner branches of the swimming feet all two- jointed, spines as in the 

 preceding species, but rather more slender. Fifth pair of feet in the male (fig. 13) one- 

 branched; first two joints of the right limb simple, third joint produced at the basal 

 angle into a stout, claw-like prominence, and armed at the apex with a long, slender, 

 curved claw, which bears three slender marginal setae ; the left limb is simple, but is 

 provided at the apex with four slender, curved, claw-like appendages, and has its margin 

 finely setose. Fifth pair of the female (fig. 12) almost rudimentary, cylindrical, slightly 

 denticulated at the apices; the penultimate joint bears an internal branch composed of 



