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Lyme Regis. This is another specialised type of structure of 
which no traces of ancestry are found in the Trias formation. 
The Crocodiles make their first appearance in the Upper 
Lias, under the remarkable form of Teleosawrus Chapmanm. 
These reptiles resemble rather the Gavial of the Ganges than 
the Crocodile of the Nile. 
Fishes played an important part in the Lias sea. The genera 
found therein are nearly all special to that formation. The 
species found in the Lower Lias are distinct from those found 
in the Upper Lias. 
It would appear from all these anatomical facts that all the 
vertebrated animals found in the Lias beds are limited to that 
formation, since we cannot discover the ancestors of either the 
marine, aerial, terrestrial or fluviatile reptiles in any of the 
older formations. 
Let us now turn to the invertebrated fossil animals included 
in the Arthropoda, Mollusca, and Radiata. Of the Arthropoda 
we have examples of Crustacea and Insecta. The Crustacea 
are represented by the genera Glyphea and Coleia, both of 
which are special forms found only in the Lias beds. Insects 
are found in the “Insect Limestone” at Aust, and the order 
Diptera of which the house fly is typical, appear for the 
first time in the Lias beds. The Mollusca afford us a very 
interesting field for observation on the advent and exit of 
species in the several stages of life into which the Lias is 
divisible. The classes into which this sub-kingdom is grouped 
being not of equal interest, the Cephalopods are specially 
selected for demonstration. These animals form the highest 
type, and one section—to which the common cuttle-fish 
belongs—have no external shell, while another section is 
furnished with a many-chambered sbell, like the Peariy 
Nautilus. Belonging to the naked section is that curious 
fossil the Belemnite, which first made its advent suddenly in 
the seas of the Lower Lias, and prevailed in such numbers 
during some of its periods that the strata containing them are 
called Belemnite beds. The Thunder-bolt (its common name) 
formed the internal skeleton of an extinct group composed 
