ISISTIUS. 237 



Squalus lichia Cuv., 1817, Reg. anim., 2, p. 130; Agass., 1835, Rech. poiss. foss., 3, pi. F, f . 7; Bonaparte, 

 ■1841, Icon. Fauna Ital., Fosci, pi. 55; Muller & Henle, 1841, Flagio.s, p. 92; Dum6ril, 1S65, 

 Elasm., p. 452; Bocage & Capello, 1866, Flagios., p. 34; Gunth., 1870, Cat. fi.shcs Brit, mus., 8, p. 

 425; Canestrini, 1872, Ital. pesci, p. 41; Gerv. & Boul., 1877, Pois.s. Fr., 3, p. 210, pi. 81, f. 28; 

 MoREAU, 1881, Poiss. France, 1, p. 358, fig. 62; Doderlein, 1881, Man. itJol. Medit., 2, p. 100. 



Squalus (Acanlhorhinus) americanus Blainv., 1830, Poiss. Fr., p. 63, pi. 15, f. 2. 



Scymnorhinus lichia Bonaparte, 1846, Cat. pesci Eur., p. 16. 



Dalatias lichia Gray, 1851, Chondropterygii, p. 75. 



Moderately slender, body cavity about three fifths and caudal fin about one 

 fourth of the total length. Snout subcorneal, bluntly rounded. Nostrils 

 anterior; valve a rounded lobe in its inner half. Eye large, orbit nearly as long 

 as the snout, longer than the distance from the spiracle. Mouth transverse 

 with a deep straight groove and with labial folds on both jaw^s at the angles. 

 A villous upper lip in front of the upper teeth is not entirely distinct. Teeth 

 dissimilar, more oblique toward the angles of the mouth, in li rows; upper lanceo- 

 late, slender, pointed, several series in function; lower broader, sectorial, with 

 triangular serrated cusp, one series in function except when about to be shed. 

 Spiracles large. Gill openings narrow, hindmost pair closer together, lower end 

 of hindmost one in front of the pectorals. Pectorals small, angles rounded, reach- 

 ing a vertical from the origin of the first dorsal. Base of dorsal short, nearly equal 

 to length of orbit, distance from the ventrals more than twice that from the pec- 

 torals, fin narrow, hind border convex. Base of second dorsal one and one half 

 times that of the first, origin above the hinder third of the ventral, hind margin 

 concave, hind angle produced, extremity reaching nearly to the caudal. Ventrals 

 moderately broad, outer angle broadly rounded. Caudal not angular, vertebral 

 axis slightly rising backward; subcaudal portion of moderate depth, not pro- 

 duced in a lobe, separated from the terminal by a shallow notch. Scales uniform, 

 small, carinate, ending in a sharp point, becoming rough in old individuals. The 

 scale crowns appear quadrangular; they have a strong median keel, also outer 

 keels near the edge which converge and unite at the angles. Some scales are 

 short and broad; on these the keel is shortened in some cases to a mere tubercle. 



Total length 22, snout to vent ISi, snout to dorsal 72, snout to pectorals 4^, 

 snout to mouth l|, and caudal 5| inches. 



Mediterranean; Atlantic. 



ISISTIUS. 



Scymnus Quoy & Gaimard, 1824, Voy. Uran., Poiss., p. 198 (part). 



Leius Kner, 1865, Denk. Akad. wiss. Wien, 24, p. 10 (non Leia Meigen, 1818). 



Isistius Gill, 1865, Proc. acad. nat. sci. Phil., p. 264. 



Body long, fusiform; tail short. Head subcorneal. Nostrils anterior; 

 nasal valve with a short process in the middle. No nictitating folds. Spiracles 



