ISOPODS OF NOKTH AMEEICA. l78 



than the l)roadth in A. ecarinata, while in ^1. tridens Leach the Unio-th 

 is onl}" two and one-half times greater than the ])readth; in the number 

 of joints in the tirst and second pairs of antennte, ten in the first pair 

 and nineteen in the second pair ))eing characteristic of ^1. fr/r/f^/A-v Leach, 

 nine in tlie Hrst 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. tr!d<^ns 

 Leach: and in the perfectl}^ smooth surface in the present species of 

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

 tricarinated. 



iEGA CRENULATA Lutken. 



jEga creniilnta Lutken, Vid. Medd. Naturh. Foren. i Kj0benhavn, 1859, i>. 70, 

 pi. A, figs. 4-5. — ScHioEDTE and Meinert, Naturh. Tidsskrift (8), XII, 

 1879-80, p. 343, pi. vii, figs. 6-9. — Miers, .Tourn. 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. V. S. 

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

 XIV, 1904, p. 434. 



Localities. — Ritenbenk and Umanek, West (irreenland; also Iceland, 

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



Parasite of Greenland shark; 

 Somniosus inici'oceplial/us. '^ b 



Body o])long - 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.: T mm. 

 Anterior margin widely rounded 

 and produced in a small median 

 point, which does not arch over 

 the antenna^ to meet the frontal fig. 154.— .t<:ga crenui.ata (after schueute and 

 lamina on the other .side. Eyes ^^'''^■^«'r)- ", young of third .tage. ?,, young 



J of second STAGE. (BoTH ENLARGED. ) 



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 tirst antenme have the two basal articles of 

 the peduncle very much enlarged; the tirst 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 Hagellum is composed of nine articles. The first antennas 

 extend to the end of the peduncle of the second pair of' antenna?, but 

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

 The tirst three articles of the second antennte are subequal; the fourth 



