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CLASS REPTILIA. 



In the imperfectly known Sphenospondylus of the English Wealden, 

 the anterior dorsal vertebrae were opisthoccelous, and all the dorsals 

 had very low neural arches. In the type genus Iguanodon, which 

 includes the largest forms, the skull (fig. 1059) is comparatively 

 short, with large and terminal nares and no teeth in the premax- 

 illa. In the typical forms, constituting the Euiguanodont group, 

 the dorsal vertebrae (fig. 1058) are amphiccelous, those in the 

 anterior part of the series having very tall neural arches and 

 compressed centra ; while the sacral vertebrae are anchylosed to- 

 gether, and have rounded inferior, or haemal, surfaces. In the 

 pelvis (fig. 1056) the ilium is shallow, with a sharply pointed post- 

 acetabular process ; while the pubis is much shorter than the 



Fig. 1057. — Inner aspect of the left femur 

 of Iguanodon bernissartensis (a), and of 

 Camptosaurus Leedsi (b). Reduced to same 

 size. «, Head ; b, Lesser trochanter ; c, 

 Inner do. ; d, Ectocondyle ; e, Entocondyle. 



Fig. 1058. — Posterior aspect of anterior dor- 

 sal vertebra of Iguanodon bernissartensis ; 

 from the Wealden of the Isle of Wight. One- 

 sixth natural size. (After Seeley.) 



ischium (which is twisted on itself), and does not form a symphysis. 

 The femur (fig. 1057, a) is characterised by the inner trochanter 

 (c) forming a crest directed almost immediately backwards, while 

 its shaft is nearly straight. The foot had only three functional 

 digits, of which the metatarsals were short and thick, and the 

 phalangeals broad and flat ; while in the manus the one phalangeal 

 of the first digit, or pollex, was modified into a stout conical spine. 

 As in the other members of the family, the astragalus, although not 



