PiECILOPODA. 153 



segment being merely somewhat widened, and furnished with 

 two projecting didactyle claws; sometimes, on account of two 

 lateral expansions resembling lobes or wings behind the thorax, 

 and of two posterior ovaries, it forms a small quadrilateral mass. 

 This tribe is composed of two genera. In the first or the 



DicHELESTiUM, Hcrm., Jun. 



We observe a narrow elongated body, slightlydilated before, and 

 composed of seven segments, the anterior of which — the thorax of 

 Herm. — is wider than the others, rhomboidal, and formed of the 

 head and a portion of the thorax united. It bears: 1, four short an- 

 tennae, of which the laieral are filiform and consist of several joints, 

 and the intermediate project like little arms and are quadri-articu- 

 lated, the last joint terminating in a didactyle claw; 2, an inferior, 

 membranous, and tubular siphon; 3, three kinds of deformed palpi — 

 two multifidfeet? — on each side, placed on an eminence; 4, four pre- 

 hensile feet, the two first of which consist of a thigh and leg ter- 

 minated by various unequal and dcntated hooks, and the others of 

 an enlarged thigh terminated by a small but stout nail. The second 

 and third segments are almost lunulated, each bearing a pair of feet 

 formed of a single joint, terminated by two kinds of toes, dentated 

 at the end. To the fourth segment is attached another pair of feet, 

 the fifth and last, but having the form of simple, oval, divergent, and 

 immovable vesicles, which Hermann presumes are rather ovaries 

 than feet. This segment, as well as the next, is nearly square. The 

 sixth is much longer, and cylindrical. The seventh and last is three 

 times shorter, almost orbicular, flattened and terminated by two small 

 vesicles. The eyes are not distinct. 



Dichelestium siurionis, Herm., Jun. Mem. Apter. p. 125, V, 

 7, 8; Desmar., Consid. L, v. About seven lines long and one 

 broad. The second segment is prolonged on each side into an 

 obtuse papilla, and the four following are red in the middle, 

 with whitish-yellow along the lateral margins. When viewed 

 from above, the feet are not visible. This animal penetrates 

 deeply into the skin and places itself on the osseous arches of 

 the branchiae, but without, as it appears, intruding upon their 

 combs. Twelve of them were taken by Hermann from a single 

 fish. Of this number, two or three, perhaps males, were one 

 third shorter than the others, and had a curved body; one of 

 the twelve lived three days. They are constantly whirling 

 about, and with considerable vivacity. By means of their 

 frontal claws they are enabled to cling with great tenacity. 

 Vol. hi.— U 



