32 THE PLAGIOSTOMIA. 



Spiracle small. Gill openings wide, in front of the pectorals. First dorsal 

 large. Pectorals falciform. Second dorsal and anal small. Many species of 

 fossil forms belonging to this family have been described from the chalk and 

 later formations. 



Gills without strainers 



teeth large, triangular, edges serrated 



without denticles at the base . . . Carcharodon (page 32) 



teeth subulate, smooth-edged 



. with or without denticles at the base . . . Isurus (page 34) 

 Gills with strainers 



teeth small, numerous, conical . . . . Cetorhinus (page 39) 



Carcharodon. 



Carcharodon Muller & Henle, 1838, Charlesworth's Mag., 2, p. 37; 1841, Flag., 70. 



Trunk fusiform, massive anteriorly; head conical; caudal peduncle strong, 

 depressed, with lateral keels and with caudal pits. Snout produced. Eye 

 medium, pupil erect; no nictitating folds. Mouth large, crescentic. Teeth 

 large, compressed, serrate, triangular, broader in the upper jaw, on which the 

 third tooth on each side is small. Spiracles small, behind the eye, sometimes 

 absent. Gill openings wide, in front of the pectorals. Pectorals large, falci- 

 form. First dorsal large, above the space in front of the ventrals. Second 

 dorsal and anal small. Caudal with vertebral axis much raised backward and 

 with a much produced subcaudal lobe. 



Numerous fossil species. Eocene and later, of this genus have been identified 

 by the teeth. Very large teeth have been secured from great depths in recent 

 dredging operations. Fossils from the Eocene, Miocene, and Pliocene have been 

 identified with species now living. 



Carcharodon carcharias. 



Plate 5, fig. 5-9. 



Lamia Rondelet, 1554, Pise, p. 390; 1558, Hist, poiss., p. 305; Gesner, 1558, Aquat., p. 204. 



Canis carcharias Aldrov., 1613, Pise. & Get., p. 383. 



Squalus No. 14, Artedi, 1738, Ichthyologia, Gen., p. 70, Syn., p. 98. 



Squalus carcharias Linne, 1758, Syst., 1, p. 235; 1766, Syst., 1, p. 400; Gmelin, 1789, Linne Syst., p. 



1498 (part). 

 White Shark, Brookes, 1763, Nat. hist., 3, Fishes, p. 28; Pennant, 1769, Zool., 3, p. 82; 1776, ibid., 



p. 93. 

 Carcharodon verus Agass., 1838, Rech. poiss. foss., 3, p. 91; 1836, ibid., pi. F, f. 3; MIjller & Henle, 



1838, Charlesworth's mag., 2. p. 37. 



i 



