53° 
SHARKS AND RAYS. 
True Dog-Fishes. 
Other Genera. 
Represented in British waters by the larger ( Scyllium canicula), 
and lesser spotted dog-fish (S. catulus), this genus is characterised by 
the first dorsal fin being above or behind the line of the pelvic pair; by the origin 
of the anal being in advance of the line of that of the second dorsal; the absence 
of serration of the upper edge of the caudal fin; and the small and delicate teeth, 
which are arranged in numerous series, and generally have a long central cusp, 
flanked by one or two small ones on each side. About half a score of species have 
been described, ranging over the coast-regions of most temperate and tropical species, 
and all of comparatively small size; the majority having prettily spotted skins. 
Their food consists mainly of crustaceans and molluscs; and their flesh is eaten 
not unfrequently by fishermen, while in the Orkneys, where the British species are 
more abundant than elsewhere, it is regularly dried for winter consumption. The 
shagreen of their skins is also employed in wood-polishing. These sharks lay eggs 
of the form shown in our illustration. Fossil dog-fishes date from the period of 
the Chalk; and they are represented in the Kimeridge Clay by the extinct 
Palceoscyllium, in which the origin of the second dorsal fin is placed in advance of 
that of the small anal. 
Among several allied genera we may especially notice the zebra- 
shark ( Steyostoma tigrinum) of the Indian Ocean, attaining a length 
of from 10 to 15 feet, and noticeable for its handsome coloration, which consists of 
a brownish yellow ground-colour, marked with black or brown transverse bars 
or round spots. In this fish the first dorsal fin is above the line of the pelvic pair, 
while the second is in advance of the line of the anal, which is approximated to 
the caudal; the latter being greatly elongated, and equal to half the total length. 
Young specimens of this shark are generally met with near the coast, but the 
adults are more or less pelagic. Dog-fishes of smaller size from the Indian Ocean 
constitute the genus Chiloscyllium, in which the first dorsal fin is either above or 
behind the line of the pel vies; while the anal is far behind that of the second 
dorsal, and close to the caudal; the teeth being small and triangular, with or 
without lateral cusps. The existing species are very handsomely ornamented with 
dark bands and spots. In a fossil state the genus has been recorded from the 
Miocene Tertiary. Three bottom-haunting sharks from the Japanese and Australian 
seas have been described under the name of Crossorhinus, and are remarkable for 
the presence of leaf-like expansions of the skin on the sides of the head. As in 
the case of other fish similarly adorned, these structures are probably for the 
purpose of attracting prey; and in order that they may be well concealed, these 
sharks have a coloration closely assimilating to that of a rock covered with sea¬ 
weed or corallines. 
The Pavement-Toothed Sharks,— Family Cesteacioxtidje. 
The well-known Port Jackson shark ( Cestrcicion philippi) and three allied 
species are the sole existing representatives of a family which was exceedingly 
abundant during the Secondary epoch. They differ from all the foregoing in 
the presence of a strong spine on the front edge of each of the two dorsal fins. 
The first dorsal fin is situated above the space between the pectoral and pelvic 
