54 THE VOYAGE OF H.M.S. CHALLENGER. 
same surface bears a very high conical oculiferous tubercle, which as a sense organ is 
quite rudimentary, being destitute of lenses, pigment, &c. A second dorsal conical 
elevation is found at the hinder margin of the cephalothorax, and similar very strong 
spines are also observed at the hinder margin of the two following thoracic segments 
(Pl. VI. fig. 5). At the point where these thorns arise the segments are a great deal 
wider than the anterior part of the following segment. The abdomen is comparatively 
long but very narrow, being only a little swollen at the extremity. The lateral pro- 
cesses for the attachment of the ovigerous legs are short, those for the true legs 
comparatively very long. 
Both specimens of this species brought up by tha Challenger are furnished with 
three-jointed mandibles. Those of the younger specimen bear at the extremity of the 
third joint slender and curved claws (Pl. VI. fig. 7); the older specimen, on the 
contrary, shows rudimentary straight and very small claws, the movable claw being 
furnished with a slender thread (Pl. VI. fig. 6). The latter specimen is a male, and 
there is no reason why it should not be considered as full-grown. 
The form of the palpi is nearly the same as in the other species of Ascorhynchus. 
The first two joints are extremely small, the third is the longest, the fourth is short, the 
fifth about twice as long, and narrow in the middle, the sixth is very short; of the seventh 
to the tenth joints, the first is the shortest, the second the longest. With the exception 
of some extremely small hairs on the last joints, the surface of the palpi is quite smooth. 
The ovigerous legs have the fourth joint the longest, the fifth shorter and swollen 
towards the extremity, the sixth about half as long as the fifth and yet more 
swollen towards the extremity ; of the four last joints the first is the longest, and the claw 
at the end of the tenth joint is extremely small. The denticulated spines are placed in 
different rows, each row showing spines of about the same size, whereas those of different 
rows vary greatly (Pl. VI. fig. 8). 
Of the legs the first pair is a great deal less developed than the three following ; its 
total length is only 30 mm., whereas that of the third pair is fully 39 mm. Of the latter 
leg the second joint is twice as long as the first or third joint, the fourth joint is the 
longest, the fifth joint is a little shorter than the fourth, the sixth again a little shorter 
than the fifth ; of the two tarsal joints the first is a little shorter than the second, the 
claw is not quite half as long as the second tarsal joint. There are no accessory claws 
(Pl. ‘VI. fig. 9). The claw of the first leg is extremely minute, yet distinct. The legs 
are almost hairless; yet the fourth and the fifth joints cannot be called smooth, as 
they are furnished with rows of knobs, corresponding with the knobs I observed on the 
lee of Mymphon hamatum, Hoek. 
The animal from which all the above measurements, &c., are taken is a male; its 
genital orifices are found ventrally on the second joint of the two posterior legs. Its 
colour is a beautiful orange-yellow. 
