STUDIES FOR STUDENTS. 
THE DEVELOLRMENT AND, GEOLOGICAL REIeA@Ns 
ONG Wale, VIEIRA VAIS) 
IOV AWE Ss 
TuHaT the birds were derived from the reptiles there is little 
doubt, the structure of the limbs, head, the thoracic and pelvic 
girdles and the feet all show a close resemblance to that of the 
same regions in the reptiles. Especially is this true in the more 
primitive birds. The general characters that are used to dis- 
tinguish the class Aves are the development of the anterior limbs as 
flying organs and the accompanying atrophy of the digits of the 
front foot ; the fusion of the bones of the skull to form a solid 
brain case; the fusion of the bones of the pelvis to form a solid 
mass of bone; the fusion of more or fewer of the dorsal 
vertebre and the development of feathers. To these characters 
there might be added for all recent birds the absence of teeth. 
In the most primitive bird that we know there is not one of these 
characters developed in anything like a complete state, except 
the presence of feathers. In fact, if it were not for the fortu- 
nate accident of the preservation of the fossil in the fine grained 
beds of the Lithographic slates of Solenhofen, so that a cast of 
the feathers has been preserved, there would be some difficulty 
in deciding the true nature of the animal. The bones of the 
head and the pelvis are not codssified; the digits of the anterior 
limb are developed with functional claws; the vertebre are 
distinct and there are many teeth in each jaw. 
The Dinosaurs have been regarded as the direct ancestors of 
the birds, both Compsognathus and Ornithonumus of the Thero- 
podous division having been considered as the forms from which 
they were derived, however there is not sufficient proof to 
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