ISOPODS OF TvTOKTH AMEEICA. 



173 



than the breadth in A. ecarinata, while in A. tridens Leach the length 

 is only two and one-half times greater than the breadth; in the number 

 of joints in the first and second pairs of antennae, ten in the first pair 

 and nineteen in the second pair being characteristic of A. tridens Leach, 

 nine in the first and ten in the second pair being true of our species; 

 in the presence of a cultriform process on the propodus of the third 

 pair of prehensile legs, which process is entirely wanting in A. tridens 

 Leach; and in the perfectly smooth surface in the present species of 

 the terminal segment of the abdomen, which in the other species is 

 tricarinated. 



^EGA CRENULATA Lijtken. 



JEga crenulata LUTKEN, Vid. Medd. Naturh. Foren. i Kj0benhavn, 1859, p. 70, 

 pi. A, figs. 4-5. ScmffiDTE and MEINERT, Naturh. Tidsskrift (3), XII, 

 1879-80, p. 343, pi. vn, figs. 6-9. MIERS, Journ. Linn. Soc. London, XV, 

 1881, p. 65. HANSEN, Vid. Medd. Naturh. Foren. i Kj0benhavn, 1887, p. 

 183. RICHARDSON, American Naturalist, XXXIV, 1900, p. 218; Proc. U. S. 

 Nat. Mus., XXIII, 1901, p. 521. NORMAN, Ann. Mag. Nat. Hist. (7), 

 XIV, 1904, p. 434. 



Localities. Ritenbenk and Umanek, West Greenland; also Iceland, 

 Finmark, and coast of Norway; in the German Sea. 



Parasite of Greenland shark; 

 Somniosus microcephahis. a 6 



Body oblong -ovate, a little 

 more than twice as long as 

 broad, 13 mm. : 28 mm. 



Head a little more than twice 

 as wide as long, 3 mm.: 7 mm. 

 Anterior margin widely rounded 

 and produced in a small median 

 point, which does not arch over 

 the antennae to meet the frontal 

 lamina on the other side. Eyes 

 large, oval, composite, and occu- 

 pying almost all the dorsal surface of the head, extending from the 

 lateral angles, along the anterior margin and meeting in the median 

 line, being contiguous. The first antennae have the two basal articles of 

 the peduncle very much enlarged; the first article is longer and a little 

 wider than the second; the second has a process at the anterior angle of 

 the distal extremity, extending half the length of the third article; the 

 third article is short and narrow, being one-third as wide as the basal 

 article. The flagellum is composed of nine articles. The first antennae 

 extend to the end of the peduncle of the second pair of antennae, but 

 not quite to the antero-lateral angles of the first thoracic segment. 

 The first three articles of the second antennae are subequal; the fourth 



FIG. 154. ^EGA CRENULATA (AFTER SCHICEDTE AND 

 MEINERT). o, YOUNG OF THIRD STAGE. 6, YOUNG 



OF SECOND STAGE. (BOTH ENLARGED.) 



LI B R 



