438 T HE WONDERS OF GEOLOGY. Lect. IV. 



The Hylaeosaurus was probably a terrestrial herbivorous 

 reptile, between twenty and thirty feet in length. The 

 modification of form in the bones composing 

 the sternal arch — in which a coracoid of the 

 lacertian type is united with a scapula like 

 that of the crocodiles — together with other os- 

 teological peculiarities, and the largely deve- 

 loped dermal processes, all combine to point 

 out the original as a most extraordinary type of 

 reptilian organization. 



As no portion of the jaw has been found, the 

 characters of the dental organs are unknown ; 

 but I have long considered the teeth before us 

 Lign. 109. {Lign. 109) as probably referable to the Hylseo- 

 Tooth of the saurus. They are generally from one inch to one 

 yl^eosaurus. an( j a k a jf i nc h long, with a cylindrical shank, 

 Forest; natural which enlarges into an obtuse, lanceolate crown, 

 size - convex in front, and depressed behind ; the 



margins of the crown are invariably worn, as if by use : 

 the internal structure consists of firm dentine, with ex- 

 tremely minute tubes radiating from the centre to the 

 periphery of the tooth, which has a thick coat of enamel.* 



44. Pterodactyles of the Wealden. — In the Weal- 

 den, numerous fragments of bones, which from their tenuity 



Very fine lines may be observed to radiate from some of the medul- 

 lary canals ; irregularly shaped, oblong, and angular radiated cells, 

 are scattered through most parts of the osseous tissue, but they present 

 less uniformity of size than do the Purkinjian cells in ordinary bone. 

 The most striking characteristics of the dermal bone, are the long, 

 straight, spicular fibres which traverse it, and decussate each other in 

 all directions, representing, as it seems, the ossified ligamentous fibres 

 of the original corium."— British Association Reports, for 1841, 

 p. 115. This description will equally apply to the internal struct ure 

 of the dorsal spines; but the latter has not yet been seen by Professor 

 Owen, as I have but very recently obtained a specimen for microscopical 

 examination. 

 * Medals of Creation, vol. ii. p. 737. 



