266 THE ANATOMY OP VEETEBKATED ANIMALS. 



any acromial process; the coracoid rounded and witliout 

 fontanelles or processes. 



No Omithoscelidan is known to have possessed a clavicle. 



The fore-limb is shorter, and often much shorter, than 

 the hind-limb. The structure of the manus is not certainly 

 known. 



The femur iisually has a strong inner trochanter ; and its 

 distal end is particularly bird-like, in the development of a 

 strong ridge, which plays between the tibia and the fibula. 



The metatarsals are elongated, and fit together in such a 

 way that they can hardly, if at all, move on one another. 

 The inner and outer digits are either shorter than the rest, 

 or quite rudimentary ; and the third digit is the longest, as 

 in birds in general. 



The Oniithoscelida are divisible into two sub-orders, the 

 Dlnosawia and the Compsognatha. The type of the latter 

 division is the wonderful little extinct reptile, Compsogna- 

 thus, which differs from the Dinosauria in the great length 

 of the centra of the cervical vertebrae, and in the femur 

 being shorter than the tibia. It has a light bird-like head 

 (provided with niimerous teeth), a very long neck, small 

 anterior limbs, and very long posterior limbs. The astra- 

 galus appears to have been ankylosed with the tibia, as in 

 birds. A single specimen only of this reptile has been 

 obtained, in the Solenhofen slates. 



IX. The Pteeosaueia. — The flying Reptiles, which be- 

 long to this group, and are commonly known as Ptero- 

 dactyls, are, and long have been, extinct, their remains 

 occurring only in Mesozoic rocks, from the Lias to the 

 Chalk inclusively. 



They are aU remarkable for their proportionally long 

 heads and necks, and for the great size of the anterior 

 limb, the ulnar finger of which, enormously elongated and 

 devoid of a claw, appears to have supported the outer edge 

 of an expansion of the integument, like the patagium of a 

 Bat (Fig. 79). 



The vertebral column is distinctly divided into cervical, 



