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). Two 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 (Selaclie) maximus}, is one of the largest of living 

 Fishes, reaching a length of 40 feet (Fig. 259). It is a pelagic 



FlQ. 259. The Basking Shark (Cetorhin us (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 Pacific to the Calif ornian 

 coast. Although generally described as a northern form, Ceto- 

 rhinus is known to occur in Australian waters. 1 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, Eec. Austral. Mus. iv. 

 1901, p. 263. 



