no. 1663. THE ISOPOD— ANCINUS DEPRESSUS — RICHARDSON. 175 



ANCINUS Milne Edwards, 1840. 



ANCINUS DEPRESSUS (Say). 



NcBsa depressa Say, Journ. Acad. Nat. Sci. Pliila., I, 1818, pp. 483-484.— Rich- 

 ardson, Amer. Nat., XXXIV, 1900, p. 224; Proc. U. S. Nat. Mus., XXIII, 

 1901, p. 537. 



Ancinus depressus Milne Edwards, Hist. Nat. Crust., Ill, 1840, p. 226, 

 pi. xxxn, figs. 17-20.— Hansen, Quart. Journ. Micr. Sci., 1905-6, p. 132.— 

 Richardson, Bull. U. S. Nat. Mus., No. 54, 1905, pp. 271-272, fig. 282.— 

 Tattersall, Fisheries, Ireland, Sci. Invest., 1904, II [1905], p. 11-18, 65. 



Body oblong ovate, twice as long as wide, 6 m «p by 121 T- Sur- 

 face smooth, punctate, and with a few markings. Color, in alcohol, 

 whitish. 



Head very wide, much wider than long, \\ vp. by 5 it is 



wider anteriorly than posteriorly, the antero-lateral angles being 

 produced in a lateral direction and 

 forming acute angles. The post-lateral 

 angles are rounded. The anterior mar- 

 gin is produced in the middle in a 

 broad, quadrangular process between 

 the basal articles of the first pair of 

 antennae, and extends forward to the 

 outer margin of these articles. It 

 meets the frontal lamina at its anterior 

 extremity. The eyes are round, com- 

 posite, and situated close to the pos- 

 terior margin of the head, but at a 

 distance from the post-lateral angle 

 equal to the width of one eye. The 

 head is coalesced with the first thoracic 

 segment about the middle, but the sides 

 are free. The first pair of antennae 

 have the basal article. large, about twice 

 as long as wide; the second article is 

 half as long as the first; the third FlG - i^Ascnrra dhbhbhb. 

 article is narrower than either of the 



first two and is one and a half times as long. The flagellum is com- 

 posed of nine articles and extends to the posterior margin of the 

 second thoracic segment. The second pair of antenna? have the first 

 article of the peduncle extremely short; the two following are sub- 

 equal and but little longer than the basal article ; the fourth and fifth 

 are also short and subeqral, being but little longer than the two pre- 

 ceding ones ; the flagellum is composed of nine articles and extends to 

 the posterior margin of the first thoracic segment. 



a All former measurements were taken from a half -millimeter scale, and 

 should be changed from millimeters to half millimeters. 



