PRESIDENTS ADDRESS. Mil, 



Expedition in the Pacific at a depth of 1,900 fathoms in company 

 with teeth of Carcharodon. In connection with the Expedition, 

 one of the most striking features of the fauna of the southern 

 temperate zone is the reappearance of types inhabiting the 

 corresponding latitudes of the Northern Hemisphere, and at the 

 same time absent in the intervening tropics. There are two 

 British species, the Larger and the Lesser Spotted Dog-fish. 



Carcharodon. Only one species of this genus is now living, 

 C. rondellelii. It is the most formidable of all the Sharks. Its 

 habits are pelagic, and it is found in all tropical and sub-tropical 

 seas, attaining a length of 4-oft. It made its first appearance in 

 the Tertiary Age. Teeth of enormous size of C. megalodon are 

 not uncommon in the Coral Crag of the Eastern Counties ; were 

 dredged up by the Challenger Expedition in the Pacific at a 

 depth of i,56oft, associated with the nodules of manganese and 

 Cetacean auditory-bones, the enamel of some of the teeth is more 

 than four inches in length along a serrated edge, and as large 

 as, if not larger, than the fossil C. megalodon. Carcharodon is 

 found in the Miocene Beds of North America, Belgium, Malta, 

 and Egypt. 



Carchariinae, Carcharias. This must not be confounded with 

 Carcharodon, dorsal fins destitute of spines ; it comprises the true 

 Sharks. It is extremely common in the tropical, less so in the 

 temperate seas. The genus comprises thirty or forty species, 

 of which the most common is the Blue Shark, C. glaucus. 

 Some attain the length of 25ft. The Tope, Galeus vulgaris, 

 is met with on the British coast ; it has a wide range in the 

 tropical and temperate regions. It is common in California and 

 Tasmania. 



The Hammer-headed Shark, Zygcena malleus, belongs to a 

 genus remarkable for the lateral extension of its skull, resem- 

 bling a hammer, which gives it the appearance of the head being 

 at right angles to the axis of the body. It is abundant in the 

 tropics. Its first appearance was in the Cretaceous Age. 



Dipnoi. The researches of Professor Huxley on the anatomy 

 of Ceratodm show that the Dipnoi, notwithstanding their 



