Sp. Char. Carapace about 2 inches 4 lines long and 1 inch 9 lines wide, all behind the nuchal sulcus marked with large semioval flattened tubereles, their blunt apices directed forwards and encircled by a crescent of small pores; the largest tubercles are about the middle of the back, and have a few small ones irregularly placed in the intervals, towards the side-margins they become smaller and more equal; anterior or cephalic portion more nearly smooth, having only small, sharp, widely separated granules, one on each side of the middle near the base and one or two in the median line near the front much larger than the rest; front margin with about three den-ticles on each side between the middle and the broad compressed horn-like processes at the angles, from each of which latter a ridge extends backwards bearing two or three strong spines; the anterior prolongation of the cheeks beneath the orbit has also a row of a few large spines: abdomen to end of caudal fins nearly twice as long as the carapace, semieylindrical, nearly smooth, with few distant punctures, the ends of the first five segments abruptly narrowed, thickened and falcately curved backwards, sixth segment having articulated to each end the two thick, elliptical, crustaceous outer marginal supports of the two outer pair of tail-fins; they are about three times longer than wide, serrated on the inner edge: first pair of feet towar the extrehers, co a lested, perionate joint drited joint forming a strong, subcompressed, curved, moveable finger, as long as the truncated end of the preceding joint, to which it is opposed for prehension, the arm about as long as the leg of the second pair; carpus about one-third the length of the arm and half the length of the hand, the width of which latter at top exceeds half its length; three next pair of legs compressed, gradually diminishing m size; fifth pair not seen. At about 2 inches from their bases the external antenna are one-fourth of an inch in diameter. 

I have great pleasure in dedicating this fine species to Mr. Bowerbank, who has done so much to illustrate the fossil botany and zoology of the London clay - his work on the former having almost created the subject; while the extraordinary extent and beauty of the collections which he has made of the other fossils of that formation are, I believe, quite unrivalled, and when fully published will demonstrate a richness in the fauna and flora of the eocene period in Britain for which few geologists are pre-pared. I have especially to record my obligations to him for sending me a large number of his choicest specimens of London-clay crustace of those species which I informed him I was about describing from the Cambridge collection, but the specimens of which at my disposal did not fully exhibit all the characters of the species; and having mentioned my anxiety to render my descriptions of those as perfect as possible, without entering further on the extensive subject of the Crustacea of that formation. The present species is usually found with the abdomen doubled close under the thorax, which latter is almost always crushed, owing to the fragile delicacy of the crust. Rare in the London clay of Sheppey (Col. University of Cambridge and Mr. Bowerbank.)