PA VEMENT- TO OTHEP) SETA EES. 
53i 
pairs; and the teeth, of which several series are in use at the same time, are more 
or less blunt and broad, more especially in the hinder part of the jaws, although 
those in each oblique row are never fused together into continuous plates. In 
PORT JACKSON SHARK (J Hat. size). 
the existing genus there is no nictitating membrane to the eye; the body is 
moderately elongated, with the second dorsal fin in advance of the line of the 
anal; and the mouth is almost or quite terminal. In the dentition, the front teeth 
are small, numerous, and 
sharp, while the hinder ones 
are broad and flattened, with a 
slight longitudinal ridge and a 
net-like ornamentation. The 
spines of the dorsal fins are 
smooth, covered on the sides 
with a thick layer of ganoin ; 
the shagreen is fine; and the 
head is devoid of spines. In 
the existing species the egg- 
capsules assume a remarkable 
screw-like form, quite unlike 
that of any other member of 
the family. The living mem¬ 
bers of the genus, none of 
which exceed 5 feet in length, 
have been recorded from the 
seas of Japan, Amboyna, lower jaw of port jackson shark nat. size). 
Australia, the Galapagos 
Islands, and California; while remains of extinct forms occur in the Cretaceous 
and Upper Jurassic strata of Europe. Very little appears to be known as to then- 
habits ; but their food is stated to consist principally of molluscs, the hard shells 
of which are crushed by the pavement-like hinder teeth. 
