GENERAL CHARACTERISTICS 



As indicated in the generic key above, differences in dentition, 

 relative placement of fins, and presence or absence of a secondary 

 caudal keel are the major criteria for distinguishing these genera. 

 All are very streamlined and characterized by a lunate caudal fin 

 with neeirly equal upper and lower lobes. The caudal peduncle is slender 

 and markedly flattened dorsoventraJ-ly, forming the prominent primary 

 keel typical of the fajnily. The gill slits are particularly long, and 

 the fifth gill opening is anterior to the origin of the pectoral fin. 

 The dermal denticles are small and quite flattened, so that the skin, 

 contrary to that of most other sharks, is relatively smooth to the 

 touch. 



Large size is attributed to all three genera of the Lamnidae. 

 For Tamna , whose members Eire the smallest, the maximum recorded is 

 about 10 feet (Bigelow and Schroeder, I9U8; Whitley, 1940). For 

 Isurus , Bigelow and Schroeder reported 12 feet (estimate based on 

 teeth), Goadby (1959) 15 feet, and Whitley (19^0) 13 feet. Straughan 

 (1958) described an encounter off the Florida coast with a shark, 

 estimated at ik to I6 feet in length, that he believed must have been 

 Isurus . However, his description suggests that it may have been 

 Car char odon. 



The white shark ( Carcharodon ) is the largest of aJ.1 predatory 

 sharks. At least one author (Goadby, 1959) stated they grow to kO 

 feet in length, and the oft-quoted record, based on an estimate from 

 teeth, is 362 feet for an Australian specimen. However, Springer 

 (1958)^ among others, is skeptical of this estimate since teeth from 

 a measured l8-foot specimen were about the size of those from the 

 Australian specimen. The largest reliable measurement (Bigelow and 

 Schroeder, 19^1-8) is 21 feet, with several others close to that figure. 

 Several estimates of over 30 feet appear in the literatiire (e. g., 

 Staxks, 1917)^ but no accurate measurements are available to sub- 

 stantiate such sizes. 



The tiger shark (Galeocerdo) closely approaches the white 

 shark in size, and the maximum recorded length actueilly exceeds 

 that for the white shark. Foiormanoir (1961) cited the capture of 

 a tiger shark in Vietnamese waters which measiired over 24 feet 

 in length (7.40 meters) and weighed over 6,800 pounds (3,110 kilograms). 



DISTRIBUTION 



Representatives of the Lamnidae are found in boreal to tropical 

 marine waters throughout the world. The white shark ( Carcharodon 

 caxcharias ) occupies a broad thermal belt. It has been reported from 



5 - 



