LAMNID^E. 301 



highest in front and with a concave upper edge ; second dorsal very small. Pectoral 

 large and falciform. Anal very small. Caudal very elongated, often equalling in 

 length the remainder of the fish, occasionally even more : its lower lobe distinct, 

 as is a notch at the end of its upper lobe. A notch at the base of the caudal fin. 

 Colours gray, dull brown, or even bluish along the back, becoming lighter 

 and occasionally of a dull white beneath. 



One 12 feet long was captured off Slapton Sands, Devonshire, in a net, 

 it was " dark blue, mottled with white over the belly " (H. Nicholls, Zool. 18G9). 



Names. Thresher, due to the use it is said to make of its tail; also slasher, 

 sea-fox, from the appearance of its tail : fox-shark, sea-ape. Llwynog-mor, Welsh. 

 Le Renard, French. 



Habits. It follows shoals of gregarious fishes, and as a consequence is mostly 

 entangled in the nets along our southern and western shores, during the mackerel, 

 herring, pilchard, and sprat seasons. One of the first English authors who has 

 remarked upon the habits of this fish appears to be Borlase, who observes that with 

 itsl ong fox-like tail, it strikes or threshes its larger and less agile enemy, the 

 grampus, whenever it ascends to the surface of the water to breathe. De Kay 

 gives the same account, adding that it pursues schools of mackerel, mossbankers, 

 and shad, and devours them in great numbers. Couch remarks that the lashing of 

 the sea with its tail, has been known to put to hasty flight a herd of sportive 

 dolphins (Delphi ui) . It has been asserted to swim round shoals of fishes, gradually 

 diminishing the size of its circles, when it uses its tail for splashing the water. 

 Mr. Blake- Knox saw one, in the winter of 1865, rise and kill a wounded diver in 

 Dublin Bay with a stroke of its tail, and then swallow it (Zool. 1866, p. 509). 



Many observers have recorded how this shark attacks whales and porpoises, 

 and their allies, and in such encounters it is assisted by sword-fishes in the warmer 

 seas, concerning which a recent author, following the views of Mr. Buckland 

 (Giinther, " Introduction to the Study of Fishes," p. 322), observes that the 

 " statements that it has been seen to attack whales and other large cetaceans rest 

 upon erroneous observations." Lord A. Campbell (Scotsman, 1880) witnessed 

 such an encounter, or at least observed from the bridge of the steamship 

 " Peruvian," off Belleisle, a fish leaping high out of the water, and which he was 

 able to see was no whale. He made a rough sketch of what he personally 

 witnessed, computing the fish's length at about 30 feet, and that of the whale as 

 much longer. The sketch shows a large fish with a heterocercal tail that sprang out 

 of the sea : the form of the tail excludes its being a cetacean, which could not 

 possibly use that appendage as a species of sledge hammer : it must therefore have 

 been a shark or a skate. " The crew of a trawler in 1878 reported a thresher 

 and sword-fish attacking a rorqual whale in Mevagissey Bay. The crew were 

 well acquainted with each of these creatures " (Dunn). As it has been abundantly 

 proved that thresher sharks do spring out of the water to strike down prey or 

 scare shoals of fishes, I think it open to doubt whether all such observations are 

 to be summarily dismissed as erroneous, until the accounts are refuted, or another 

 agent is convicted of the assaults in question. Mr. Layard (Land and Water) 

 asserts having witnessed such a conflict on more than one occasion, and to have 

 been so near as to see very distinctly, that besides the assailant which was 

 pummelling the unfortunate whale from above, there was more than one attacking 

 it from below. He asserts he knows the thresher shark well, and it was certainly 

 one of the aggressors in the fight he once witnessed off the Cape of Good Hope. 

 Many other authorities have likewise seen these encounters, as Mr. Pascoe and 

 Mr. Howard Saunders. Couch found some young herrings in the stomach of the 

 one he examined, and Mr. Gerrard twenty-seven mackerel in another, 13| feet 

 long, from Folkestone. 



Means of capture. In olden times, says Pennant, it was believed that when it 

 had the misfortune to have taken a bait, it swallowed the hook until it arrived at 

 the cord, which it severed with its teeth, and so escaped. Is rarely captured off 

 our shores with a baited hook ; and Oppian asserts that the lower portion of the 

 line was formed of hair, while, to guard the hook from being cut away, the line 

 for some distance above it was armed, or, remarks Couch, as the fishermen now 



