Descr. Carapace very nearly as broad as long, coarsely granulated ; frontal margin nearly straight, denticulated; the rostrum flattened, somewhat expanded, bidentate ; orbits placed near the external angle, but not at the extremity as in Thenus; upper and inner orbital margin elevated; cervical furrow deep, smooth, commencing on the lateral margin, about one fourth from the anterior angle, and passing obliquely backwards to about the middle of the carapace; gastric region with an elevated ridge on the centre having two angular projections, of which the posterior is the more prominent, and a small tubercle on each side; cardiac region with a strong ridge similar to that of the gastric, terminating abruptly at the cervical furrow; branchial region with two slightly tuberculated ridges, the outer one marginal. Basal joints of the external antenne broad and flattened, as in the other genera of this family; abdomen rounded, raised in the centre, but not carinated; the segments granulated, excepting on that portion of each which passes under the one in front of it.

In all the specimens yet discovered, the abdomen is bent under the thorax. Length of carapace, 1.4 inch; breadth, 1.4 inch nearly.

 Obs. All the specimens hitherto obtained of this species are from Sheppey. The original one, to which further allusion will presently be made, is in the British Museum, There are four in the collection of Mr. Bowerbank, and one in that of Mr. Wetherell. In all of these the limbs and the caudal extremity of the abdomen are either wholly wanting or existing only in unavailable fragments. There are, however, sufficiently perfect remains of other parts, to afford data for its association with Zhenops in the family Scyllaride, and for its generic distinction from that and from the recent forms of the family. Its nearest approximation is to the recent genus Scyllarus, from which it is sufficiently distinct by the form of the rostrum, the depth and distinctness of the cervical furrow, and the rounded form of the abdomen. Its relation to that genus is, however, very obvious in the position of the eyes, in which it differs from the other two recent genera of the family.

 The literary history, if it may be so termed, of this species, is somewhat curious. A single specimen only was known to be in existence, until those above referred to were found to be contained in the rich collections of Mr. Bowerbank and Mr. Wetherell. That specimen is now, and has been for very many years, in the British Museum. It formed the subject of a description with a figure by the late M. Konig im his ‘ Icones Fossilium Sectiles, under the name of Scyllarus(?) tuberculatus. 'This proves, on examination, as was first pointed out to me by Mr. Woodward, to be artificially made up; the whole surface of the carapace is fictitious, and the very tubercles* on which the name was founded exist only in obedience to the skill and trickery of the artist. All the distinctive characters, even of the family to which it belongs, are thus lost, but Mr. Komg with great acumen recognised its affinities from its general form, and named it as above. In Professor Morris’s most useful and elaborate ‘ Catalogue’ it is mistakenly referred to the Brachyurous genus Xanthopsis, as a synonym of Z. nodosus, of M‘Coy, simply, as I presume, from its specific name fwberculatus; and this oversight probably arose from the specimen not having been seen, and the figure itself having been forgotten by the learned author. The specific name, having been founded on an error, must be changed; and I have great pleasure in the opportunity afforded me of naming it after my old friend Mr. KÖnig, who first distinguished it, and appreciated its relations.