228 THE ANATOMY OF VERTEBKATED ANIMALS. 



No Ornithosoelidan 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 usually 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 

 iimer 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 Ornithoscelida are divisible into two sub-orders, the 

 Dinosauria and the Oompsognatha. The type of the latter 

 division is the wonderful little extinct reptile, Compsogna- 

 ihus, 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 numerous teeth), a very long neck, small anterior limbs, 

 and very long posterior limbs. The astragalus appears to 

 have been anchylosed with the tibia, as in birds. A single 

 specimen only of this reptile has been obtained, in the Solen 

 hofen slates. 



IX. The Pteeosaueia. — The iiying Reptiles, which belong 

 to this group, and are commonly known as Pterodactyls, are, 

 and long have been, extinct, their remains occurring only in 

 Mesozoic rooks, from the Lias to the Chalk inclusively. 



They are all 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 expan- 

 sion of the integument, like the patagium of a Bat (Fig. 79). 



The vertebral column is distinctly divided into cervical, 

 dorsal, sacral, and caudal regions, the cervical vertebras being, 

 as in Birds, the stoutest of all. The atlas and axis are anchy- 

 losed together, at least in the cretaceous species. The other 

 cervical vertebrae, apparently not more than six or seven in 

 number, have low, or obsolete, spinous processes ; and, like 

 the vertebrae of the rest of the spine, are proccelous, and 

 have the neuro-central suture obliterated. The existence of 

 cervical ribs is doubtful. From fourteen to sixteen vertebras 

 intervene between the cervical and the sacral regions ; and 

 not more than one or two of the hindermost of them, if any 



