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numerous remains of teleosaurians have been discovered, being 
well adapted for aquatic life, with their long jaws, sharp-pointed 
teeth, and bi-concave vertebra best fitted to pursue and seize 
slippery prey like-fishes. In form, these reptiles differed but little 
from the modern gavials, having a similar long, slender snout and 
sharp-pointed teeth. The fore-limbs were much smaller than the 
hinder ones. ‘The vertebree were bi-concave, and the upper and 
under sides of the body encased in armour as a _ protection 
against the large contemporary carnivorous marine /chthyosaurti 
and other forms. ‘The opening of the posterior nares upon the 
palate is not so near the snout as in the Triassic genera and the 
external nostril has but one aperture. In the middle Purbeck 
beds of the later Mesozoic epoch, dwarf crocodiles have been 
discovered, and were subsequently described by Professor Sir 
Richard Owen, one under the name Brachydectes, or short biter, 
owing to the fact that only one third of the alveolar border is 
provided with teeth, the hinder part being edentulous. ‘The 
other Zheriosuchus is better known from a well-preserved skull 
and nearly complete skeleton. It appears it rarely attained a 
length of more than eighteen inches when adult. Other remark- 
able features characterise these dwarf crocodiles and Gonzopholis 
from the Wealden deposits. The posterior nares were placed 
further back on the palate ; the skull is broader, and the centres 
of the vertebra are not so concave as in the earlier species, but 
are nearly flat. The armature was also different. ‘The dorsal 
scutes had a peg which fitted into a groove of the succeeding 
scute; the ventral scutes were firmly joined together by broad 
scutral borders. A similar structure is characteristic of the large 
bony enamelled scales of many of the ganoid fishes, among which 
we may name the American gar-pike (Lepidosteus). Seven 
specimens of this genus, thanks to Colonel Marshall McDonald, 
U.S. Fish Commissioner, can now be seen alive in tank fifteen of 
the Brighton Aquarium. In the middle Mesozoic, from the 
Stonesfield slate, at the base of the Great Oolite to the close of 
the Cretaceous, many more genera and species of mammalia 
made their appearance, ranging in size from a mole to a pole-cat. 
The later middle Purbeck beds of Durdleston Bay have yielded 
twelve other species, and in the upper Cretaceous of Dakota and 
Wyoming, U.S.A., Professor O. C. Marsh has quite lately dis- 
covered about roo specimens representing many species, varying 
in size from a mouse to an opossum. This increase in the 
mammalian fauna affording a change of diet and necessitating 
increased activity in pursuit of these small mammals might have 
promoted variations in the form of the vertebra and the further 
backward prolongation of the posterior nares in the Purbeck, 
Wealden, and upper Cretaceous crocodilia. 
A great break occurs at the close of the Wealden deposits. 
