OCR Text |
Show 1867.] MR. J. Y. JOHNSON ON NEW CRUSTACEANS. 899 The jaws are powerful, each consisting of an external cutting edge and a tuberculated crushing-apparatus inside. On the upperside of the mouth there is a large membranous lip. The sternum is very narrow, and between each of the fourth and fifth pairs of legs there is a large transverse deltoid tooth. All the ambulatory legs are slender and unarmed, except by their terminating nails; the order of their length is 3, 5, 4, 2, 1, those of the third pair being the longest. The legs of the three anterior pairs are didactyle, with smooth hands and slender fingers. On the underside of the first pair of legs are some long bristly hairs. The two posterior pairs are monodactyle. None of the members are multiarticulate. To the basal joint of all except those of the last pair is attached a lamellar appendage, which lodges under the carapace. The abdomen is hairless, shining, sparsely puncturate, subcom-pressed in front, much compressed behind; the sides of the segments project over the bases of the false feet. On the third segment commences a low median crest, which becomes more and more conspicuous on the posterior segments ; and this crest projects a small tooth at the posterior border of the third, fourth, fifth, and sixth segments. The three anterior segments are marked by a deep transverse groove in their anterior halves; and there is a small notch at each side of the posterior border of the first, second, fourth, and fifth segments, whilst at the same place on the sixth there is a large rounded lobe. A small tooth is seen at the posterior angles of the segments from the second to the sixth inclusive. The false feet of the five anterior segments are well developed; their peduncles are stout; and all (except in the case of the first) carry two many-jointed ciliate palpi, one of which is much longer than the other. The single palp of the first pair of false feet is longer than the other palps. The inferior surface of the abdomen is covered with membrane. Between the bases of the first three pairs of false feet there is a deltoid process terminating in a tooth. The middle caudal plate or seventh abdominal segment is narrow, and terminates in a spine; its sinuous borders are fringed with hair. The middle of the upper surface is depressed, and the sides are marked by two low ridges. The lateral swimming-plates are narrowly oval, and extend beyond the middle plate; those of the outer pair are fringed with hair on the inner edge, whilst the upper surface is marked with two longitudinal furrows near the outer margin, and there is a small spine on the outer edge near the extremity. The inner pair of plates are fringed with hair on both edges. At the middle of the upper surface there are three longitudinal furrows. A single specimen of this fine crustacean, the largest and handsomest of its genus, was obtained at Madeira, where it appears to be of rare occurrence; but in the fish-market of Algiers I have frequently seen considerable quantities of a red Peneeus which, after careful examination, I do not hesitate to assign to the same species, notwithstanding a few differences of minor importance. |