RHINCODON. 41 



the first dorsal. Second dorsal and anal small, nearly ecjual, anal base the 

 farther back, origin below the hind part of the second dorsal, (audal peduncle 

 depressed, with lateral folds and with pits at the root of the caudal fin. Caudal 

 fin large, vertebral axis much raised backward, a notch behind the subcaudal, 

 subcaudal lobe produced, sharp. Reaches a length of thirty- five feet or more. 



Back greyish brown; lower surfaces white. 



Arctic Seas to the temperate regions. 



Rhincodontidae. 



This family contains a species of large shark, the affinities of which place it 

 near Cetorhinus. It approaches that genus in its enormous size, large mouth, 

 small eyes, small spiracles, small teeth, large pectorals, in the sizes and propor- 

 tions of dorsals and anal, in the erected caudal, the caudal pit and the develop- 

 ment of the subcaudal lobe. It has nasoral grooves, and has keels on the body 

 as on some of the Orectolobidae, but it differs from them in lacking nasal cirri, 

 in size, in the disproportions of pectorals and dorsals, in the erected supracaudal, 

 the lobed subcaudal, and the lateral keels of the caudal pedicel. 



Rhincodon. 



Rhincodon A. Smith, 1829, Zool. journ., 4, p. 443. 



Rhineodon Muller & Henle, 1837, Wiegm. archiv., 1, p. 84; Swains., 1839, Class, 2, p. 314; Jord. & 



Fowler, 1903, Proc. U. S. nat. mus., 26, p. 626. 

 Rineodon Muller & Henle, 1838, Charlesworth's mag., 2, p. 37; Swains, 1838, Class., 1, p. 142. 

 Rhinodon Muller & Henle, 1841, Plagios., p. 77; A. Smith, 1849, Afr. Pisces, pi. 26; Gunth., 



1870, Cat. fishes Brit, mus., 8, p. 396. 

 Micristodus Gill, 1865, Proc. Acad. nat. sci. Phil., p. 177. 



Subfusiform. Head depressed; snout broad, blunt. Eyes small, lateral, 

 near the angle of the mouth, without a nictitating membrane, lower lid with- 

 out a fold. Spiracles small, lateral. Nostrils anterior, grooved to the mouth, 

 without cirri. Mouth large, anterior, with labial folds on both jaws. Teeth 

 very small, very numerous, subcorneal, curved. Gill openings wide, hindmost 

 narrower, two above the pectoral. Pectorals large, falciform. Two dorsals, 

 without spines, with produced angles; anterior near the middle of total length, 

 much the largest, separated by more than the length of its base from the 

 second dorsal. Anal very small. Tail with a pit at the origin of the supra- 

 caudal, which latter is erected as .in Isuridae; subcaudal with a well developed 

 lobe; pedicel with a keel at each side. 



Pacific and Indian Oceans. 



