XVII ELASMOBRANCHII—-SELACHII 453 
become extinct is proved by the fact that similar teeth have been 
dredged from the bottom of the Pacific. Teeth and detached 
vertebrae from various Tertiary deposits have been referred to 
species of Alopecias. Entire Fishes, with an elongated rostrum 
and an extensive anal fin, from the Cretaceous of Mount 
Lebanon, have been assigned to an extinct genus, Scapanorhynchus. 
Fam. 11. Cetorhinidae (Basking Sharks).—T wo dorsal fins, 
without spines, the anterior midway between the pectoral and 
pelvic fins. Tail without lateral keels. Nictitating membranes 
absent. Spiracles small, situated just above the angles of the 
mouth. branchial clefts wide and of great vertical extent, 
extending from the dorsal to the ventral surface. Teeth small, 
very numerous, conical in shape, without serrations. Claspers of 
the male provided with horn-like denticles. 
The single species included in this family, the Basking Shark, 
(Cetorhinus (Selache) maximus), is one of the largest of living 
Fishes, reaching a length of 40 feet (Fig. 259). It is a pelagic 
A 
Fic. 259.—The Basking Shark (Cetorhinus (Selache) maximus). 
(From Goode and Bean.) 
Shark, inhabiting the Arctic seas, but wandering as far south on 
opposite sides of the Atlantic as the Mediterranean, the coasts of 
Portugal and Virginia, and in the Pacitic to the Californian 
coast. Although generally described as a northern form, Ceto- 
rhinus is known to occur in Australian waters! It is fairly 
common off the coasts of Scotland, and it has been seen or 
captured at various points on the western coast of Ireland, and 
1 Kershaw, Victorian Natural. xix. 1901, p. 62; Waite, Rec. Austral. Mus. iv. 
1901, p. 263. 
