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



same surface bears a very high conical oculiferous tul^ercle, which as a seusc 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 l)ut very narrow, being only a little swollen at the extremit}-. The lateral pro- 

 cesses for the attachment of the ovio;erous leas are short, those for the true legs 

 comparatively very long. 



Both specimens of this species brought up l)y the Challenger are furnished with 

 three-jointed mandibles. Those of the younger specimen bear at the extremity of the 

 thii'd 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 (PI. VI. fig. 6). The latter specimen is a male, and 

 there is no reason why it should not be considered as fuU-gro'uai. 



The form of the palpi is nearly the same as in the other species of Ascorhynclms. 

 The first two joints are extremely small, the third is the longest, the fourth is short, the 

 fifth about twAcQ 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 

 difi"erent rows, each row showing spines of about the same size, whereas those of difi"crent 

 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 quite 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 

 leg of Nymjyhon hamatnm, Hock. 



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. 



