1204 



CLASS REPTILTA. 



have been an allied genus. In the Lower Liassic genus Dimorph- 

 odon (fig. 1 1 o i ) the jaws are toothed to their anterior extremities, 



and the hinder teeth of the man- 

 dible are much smaller than those 

 in front. Both the nares and pre- 

 orbital vacuities are of enormous 

 size, and are separated by a narrow 

 bar. The coracoid is anchylosed 

 to the scapula; and the astragalus 

 united to the tibia. Dimorphodon 

 is thus the earliest known represen- 

 tative of the order ; and the one 

 species attained considerable dimen- 

 sions. Its remains occur in the Liassic 

 shales of Lyme Regis in Dorsetshire, 

 and were first brought to notice in 

 1822 by the indefatigable Dean Buck- 

 land. 



Ordinal Position Uncertain. — 

 Here may be noticed a genus of which 

 the serial position must for the present 

 remain undecided. It is known as 

 Ornithodesmus, and was founded upon 

 an imperfect sacrum from the English 

 Wealden, which has been regarded as 

 Avian, although its right to distinc- 

 tion from the Ornithosauria appears 

 by no means certain. It may be 

 observed that the so-called Ornitho- 

 pterus, of the Upper Jurassic lime- 

 stones of Bavaria, said to be char- 

 acterised by the presence of only two 

 digits in the ulnar digit of the manus, 

 and which has been regarded as 

 Avian, appears to have been found- 

 ed upon an imperfect specimen of 

 Rhamphorhynchus ; and it may also 

 be mentioned that the name Orni- 

 thopterus is preoccupied by the Lepi- 

 dopterous genus Ornithoptera. Fin- 

 ally, it has been suggested that a 

 tooth from the Trias of Italy de- 

 scribed under the name of Tribelesodon may indicate an Ornitho- 

 saurian at that early period, but the evidence in support of that 

 view is at present wholly insufficient. 



the 



Fig. 1101. — Restored skeleton 

 Dimorphodon macronyx ; from 

 Lower Lias. Reduced, f, Ulnar digit ; 

 m, Other digits ; p, Metatarsus. (After 

 Owen.) 



