REPTILIA. 



55 



a dinosaurian femur with lacertian teeth, and are usually reckoned 

 among the " Lacertilia," are found as low as the Trias. The " An- 

 omedontia " (as the Rhynchosaurus) also belong to this group, and are 

 Triassic. They have generally no teeth or only a pair of tusks, bicon- 

 cave vertebrae, a single condyle, long curved trunk ribs, a complete zy- 

 gomatic arch, and ambulatory limbs. 



Dinosaurians. 



No. 200. Iguanodon Mantelli, Meyer. 



Lower Jaw. This great Dinosaurian 

 was brought to light by Dr. Mantell in 1834. 

 It was an oviparous, herbivorous, terrestrial 

 quadruped, " a crocodile-lizard of the dry 

 land." It occupied in the Eeptilian Age the 

 same relative station in the scale of being, 

 and fulfilled the same general purposes in 

 the economy of nature, as the Mastodons, 

 Mammoths, and Megatherioids of the Pleis- 

 tocene Period, and the existing gigantic Pachyderms. Fragments of coniferous 

 trees, arborescent ferns and cycadeous plants have been found with its remains, 

 showing the nature of its food. Professor Owen estimates the length of the head at 

 three feet, of the trunk at twelve feet, and of the tail at thirteen feet. The I. had 

 large hollow limb-bones and unguiculate feet — the hind pair, at least, having only 

 three well-developed toes. The vertebra?, subconvex anteriorly in the neck but 

 along the trunk subconcave on both surfaces, were articulated by a ligamentous sub- 

 stance as in Mammals. The dorsals are distinguished by their lofty and expanded 

 neural arches ; the sacrals by their unusual number (six) and complexity ; and 

 the caudals by neural spines of great height. The teeth differ in structure from 

 those of every known Reptile. They are characterized by the prismatic, slightly 

 curved form of the crown, the presence of from two to four longitudinal ridges on 

 the enamelled face, and the serrated margins and summit. The teeth of the 

 upper jaw are curved in the opposite direction to those of the lower, and have 

 the convexity external. None of the teeth are fixed in distinct sockets, but are 

 soldered by one side of the fang to the internal surface of the jaw. The cranium 

 has not yet been discovered. This almost perfect specimen of the lower jaw is 

 interesting, showing as it does that in the small extent of the symphysis the 

 Iguanodon resembles the Lizards, and differs from the Crocodiles, while in the 

 position of the symphysis and its sloping edentulous character the Iguanodon 

 differs from all modern Reptiles. It was found in the Wealden strata, Sussex, 

 England, and belongs to the British Museum. Size, 20x11. Price, $6.00. 



Ne. 201. Iguanodon MantelH Meyer. 



Lower Jaw, left e Ajrus (young). This fragment was found in the Tilgate 

 Forest (Wealden), England, and is in the British Museum. Mantell ascribes it to 

 the Regnosaurus Nortliam'ptoni, a small lacertian Reptile allied to the Iguanodon; 



