The thorax and prosoma are of the same shape as in _I. Cumingii_, and in the largest specimen, about one tenth of an inch square; the prosoma, as in that species, is hairy. In the _Mouth_, all the parts are closely similar to those of _I. Cumingii_, but one third larger; the crest of the labrum is a little roughened with minute points: the palpi are squarer and blunter at their extremities: the mandibles have their second and third teeth nearly equal in size to the first, and they do not appear pectinated: the maxillæ have their spinose edge very nearly straight: the outer maxillæ are pointed. The olfactory orifices are similarly situated, and of similar shape; they are dark coloured. _Cirri._--These also are similar to those of _I. Cumingii_; the segments, however, of the three posterior cirri have each four pair of spines, placed very close together in a transverse direction. First cirrus has its two rami unequal in length by about six segments. The anterior rami of the second and third cirri are thicker, and more thickly clothed with spines, than the posterior rami, to perhaps a greater degree than in _I. Cumingii_. In the posterior cirri, the upper segments of the pedicels are nearly as long as the lower segments. _Caudal Appendages_, four times as long as the pedicel of the sixth cirrus, and three fourths of the length of the rami of this same cirrus: segments thirty-two in number, and therefore as many as those forming the sixth cirrus: the upper segments are much thinner and longer than the basal segments; each furnished with a circle of short bristles; whole appendage excessively thin and tapering: the two closely approximate. _Colour._--From some well-preserved dryed specimens in Mr. Stutchbury’s possession, it appears that the sack, cirri and trophi, were dark blue, as in _I. Cumingii_; after being long kept in spirits, these parts become brown.