5 2 4 
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 
H^iinni6rli3dids ~ ^ 
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 no 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. 
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 those 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 
Hounds. 
