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



The pleon is long and gradually narrows posteriorly ; a strong tooth stands in the 

 median line on the ventral surface of each of the five anterior somites (see fig. 2), 

 gradually diminishing in size from the first, where it is long and strong, to the fifth, 

 where it is little more than a sharp prominence, while there is no trace of it on the 

 sixth. 



The pleopoda are short and articulate with the fixed coxal process of each somite 

 near the lateral extremity. The first pair (p) has two unequal rami, one branch being as 

 long as the basal joint, and the other about half its length, the inner being destitute of 

 hairs. The second (q) and three following pairs are similar to each other, and consist of 

 two subecmal foliaceous branches fringed with long hairs, and bearing a small stylamblys 

 on the inner branch. 



The ultimate pair helps to form the rhipidura and is implanted beneath the telson, 

 and when compressed the appendages impinge longitudinally against each other in the 

 median line. The outer plate is the shorter, and terminates subapically on the outer 

 side in a small tooth ; the inner plate is more tapering and reaches as far as the extremity 

 of the telson. 



Observations. — This species may easily be distinguished from Pontocaris propensalata 

 by the extension of the fronto-lateral wing-like processes in an oblicmely outward direc- 

 tion, instead of directly forwards. 



The carapace has the same number of carinas, similarly situated, but the infero-lateral 

 ridge is more decided in character. The rostrum is bifurcate at the extremity in the 

 described specimen, which is a female. There are two others in the collection that closely 

 resemble the type ; one has the rostrum rounded as if the two apical points had been 

 rubbed down, the third, which I take to be a male, is somewhat more slender in form, 

 less corrugated generally, and has the outer ramus of the first pair of antennas much 

 more robust ; in this specimen the rostrum is sharp pointed and the teeth at the base are 

 obsolete. The posterior margin of the carapace is more compressed than the anterior, and 

 the lateral carina has only two rudimentary denticles posterior to the three or four large 

 ones at the anterior extremity. The dorsal carina on the pleon is interrupted, and the 

 corrugations are as prominent as those of the preceding species, but slightly different in 

 form. The ophthalmopoda are larger, but the oral appendages and pereiopoda are 

 very similar. The large tooth on the ventral surface of the pereion in Pontocaris 

 2?ropensalata is wanting in Pontocaris pcnnata, but in both species laterally 

 compressed teeth are present on the ventral surface of the pleon. The general 

 character of the integumentary structure is strong and rigid, much more so than we 

 find in any of the species of the genus Crangon, and corresponds more with that of 

 the genus Glyphocrangon, from which, however, it differs in several essential points of 

 structure. 



