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 termina- 

 ting 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 seg- 

 ments project over the bases of the false feet. On the third seg- 

 ment 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 trans- 

 verse 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 aiiterior 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 mem- 

 brane. 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 sur- 

 face there are three longitudinal furrows. 



A single specimen of this fine crustacean, the largest and hand- 

 somest of its genus, was obtained at Madeira, where it appears to be 

 of rare occurrence ; but in the fish-market of Algiers I have fre- 

 quently seen considerable quantities of a red Penceus which, after 

 careful examination, I do not hesitate to assign to the same 'species, 

 notwithstanding a few differences of minor importance. 



