ROOM III. DINOSAURIAN REPTILES. 225 



of five ! vertebrae of unusual construction ; by the height, 

 breadth, and outward sculpture of the neural arch of the 

 dorsal vertebrae ; by the two-fold articulation of the ribs to 

 the vertebrae, viz. at the anterior part of the spine by a 

 head and tubercle, and along the rest of the trunk by a 

 tubercle attached to the transverse process only ; by broad, 

 and sometimes complicated, coracoids, and long and slender 

 clavicles, whereby Crocodilian characters of the vertebral 

 column are combined with a Lacertian type of the pectoral 

 arch. The dental organs also exhibit the same transitional or 

 connecting characters, in a greater or lesser degree. The bones 

 of the extremities are of large proportional size for saurians ; 

 they have large medullary cavities, and with well developed 

 and unusual processes, and are terminated by metacarpal, 

 metatarsal, and phalangeal bones, which, with the exception 

 of the ungual phalanges, more or less resemble those of the 

 heavy pachydermal mammalia, and attest, with the hollow 

 long-bones, the terrestrial habits of the species. 



" The combinations of such characters some, as the sacral 

 ones, altogether peculiar among Reptiles others borrowed, as 

 it were, from groups now distinct from each other and all 

 manifested by creatures far surpassing in size the largest of 

 existing reptiles, will, it is presumed, be deemed sufficient 

 ground for establishing a distinct tribe, or sub-order, of 

 Saurian Reptiles. 



" Of this tribe, the principal and best established genera 

 are the Megalosaurus, the Hylceosaurus, and the Iguanodon ; 

 the gigantic Crocodile-lizards of the dry land ; whose peculiari- 

 ties of osteological structure distinguish them as clearly from 

 the living terrestrial and amphibious Saurians, as the opposite 

 modifications for an aquatic life characterise the extinct Ena- 

 liosauriaTis, or marine lizards." 2 



The remains of these animals are chiefly found in the Weal- 

 den deposits ; but of the first-mentioned genus, the Megalo- 

 saurus, the most important parts of the skeleton have been 

 obtained from the lower oolitic strata at Stonesfield, near 

 Oxford ; and of the Iguanodon, a highly interesting specimen 

 has been discovered in the greensand of the Chalk formation, 

 near Maidstone. 



1 The sacrum of the Iguanodon is composed of six vertebras. 



2 " British Assoc. Report on Fossil Reptiles," 1841, p. 144. 



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