524 SHARKS AND RAYS. 



Our next representative of the family is the small shark 

 commonly known as the tope (Galeus canis), which belongs to a 

 genus including only two species and characterised as follows. The muzzle is 

 short and the mouth crescent-shaped ; very small spiracles are present ; there is no 

 pit at the root of the caudal fin, which has only a single notch ; and the teeth, 

 which are similar in the two jaws, have serrated edges, and a notch on the hinder 

 border. The common tope, which is usually about 6 feet in length, although it 

 may grow to 7 feet, is a very widely spread species, ranging over all temperate 

 and tropical seas, and visiting the shores of such widely separated localities as 

 California, the British Islands, and Australia. In colour it is dark grey above, 

 and dirty white beneath. The second living species inhabits the Japanese seas ; 

 and teeth from the Tertiary formations of Europe have been referred to the 

 genus. In habits the tope is a bottom-haunting species especially during the 

 winter months and devours other fish, crustaceans, and star-fishes. It is not 

 unfrequently taken by the line, and is thus a great source of annoyance to fisher- 

 men, especially on the Norfolk coast, where considerable numbers are sometimes 

 hooked. The young are produced alive, and it is stated that there have been 

 instances of as many as fifty individuals in a single brood. 



Having teeth very similar to the true sharks, the five species 

 Hammerheads. 



known as hammerheads, or hammer-headed sharks, one of which 



(Sphyrna malleus) is represented in the illustration on p. 521, form a genus unique 

 among fishes in the extraordinary conformation of the head. Instead of retaining 

 the usual more or less pointed form, the front part of the head of these sharks 

 is broad, flattened, and expanded on each side into a process, on the flat terminal 

 surface of which is situated the eye. This, of course, is quite sufficient to dis- 

 tinguish the genus ; but it may be added that the caudal fin has a single notch 

 and a pit at its root, there are 110 spiracles, the nostrils are situated on the 

 front edge of the head, and the mouth is crescent-shaped. The teeth differ from 

 those of the true sharks in being similar in both jaws ; their margins being either 

 smooth or serrated. Hammerheads range over all the warmer seas, the common 

 species being sometimes taken on the British coast ; and an extinct form occurs 

 in strata of Miocene age. Growing to a length of some 14 or 15 feet, the common 

 hammerhead is one of the most formidable and voracious of its tribe, and is much 

 feared in the Indian seas. 



und By this somewhat inappropriate title are designated two small 



British sharks, one of which (Mustelus Icevis) is shown in the lower 

 figure of the accompanying illustration. Externally these sharks are not unlike 

 the tope, but the snout is less pointed. As a genus they are characterised by the 

 rather short muzzle ; the crescent-shaped mouth ; the presence of minute spiracles ; 

 the absence of a pit at the base of the caudal fin, which has scarcely any lower 

 lobe; and the slight difference in the size of the two dorsal fins. The teeth, 

 moreover, are small and numerous, being either blunt or with indistinct cusps, 

 and forming a kind of pavement-like structure ; those in the upper jaw being 

 similar to these in the lower. The smooth hound, which is the species here 

 figured, is generally about 4 feet in length, although it may reach to 6 feet. The 

 sides of the back are marked by a series of whitish spots, more distinct in 



