PISCES. 
69 
Gault, only differs from Hybodus in its blunter teeth (Fig. 69). Table-case 
Paldeospinax, from the Upper Lias of Wurtemberg, is a small 5 - 
allied shark with smooth dorsal fin-spines and with simple 
vertebrae (Wall-case 3). Synechodus from the Chalk is nearly 
Fig. 66. —The existing Port Jackson Shark (Cestracion philippi), from 
Australian seas; much reduced. sp\ anterior dorsal fin-spine; sp". 
posterior dorsal fin-spine. 
Fig. 67. Jaw of Port Jackson Shark (Cestracion philippi), showing 
grasping teeth in front, crushing teeth at the sides. (Table-case 5.) 
similar (Table-case 5). Aster acanthus, with a dentition com¬ 
monly named Strophodus (Fig. 70), agrees with Hybodus and 
Acrodus in most essential respects. As shown by good 
specimens from the Oxford Clay of Peterborough in Table- 
case 5, the head was armed with the so-called Sphenonehus. 
