IGUANIANS. 243 



The Amblyrhynchus, a genus which is somewhat remarkable for 

 the marine habits of at least one of the species, {Amhlyrhynchus ater) 

 whose diet is sea-weed, (1) has the tricuspid structure well developed 

 in the posterior teeth, and these teeth are somewhat thicker than in 

 the preceding Iguanians. 



The typical genus of the present family of Saurians is characte- 

 rized by the crenate or dentated margin of the crown of the maxillary 

 and premandibular teeth, a few of the anterior small ones excepted ; 

 the pterygoid teeth are arranged in two or three irregular rows, re- 

 sembling somewhat the ' dents en cardes' of fishes. 



In the full-grown Iguana tuberculata there are from forty-seven to 

 forty-nine teeth in both upper and lower jaws : the number is less in 

 young subjects. The double row of pterygoid teeth are in close order 

 on each side. 



In the horned Iguana {Metopoceros cornutus, d. & b., PI. 70, 

 figs. 6 and 7) there are about fifty-six teeth in both the upper and 

 lower jaw, of which the four first are conical and slightly recurved ; 

 the twelve succeeding teeth are somewhat larger in size, with more 

 compressed and expanded crowns ; the rest are triangular, compressed, 

 with dentated margins. The inner surface of the crown of the tooth 

 is simply convex and smooth, the outer surface traversed by a median 

 longitudinal broad obtuse ridge. 



There is a single row of small teeth implanted in each pterygoid 

 bone (PL 68, fig. 2, d). No Iguanian lizard has teeth on the palatine 

 bones. (2) 



The teeth of the Cycluri differ from those of the Iguanas in being 

 trilobate or bilobate and not crenate at the margin : the pterygoid 

 teeth are in a single row. 



In the Iguana cyclura of Cuvier there are thirty- six teeth in the 



(1) This species, and probably all the known Amhlyrhynchi or blunt-nosed Iguanee, inha- 

 bit the islands of the Gallopagos group ; their habits have been well elucidated by Mr. Darwin, 

 (Voyage of the Beagle, vol. iii. p. 466) : in specimens which he dissected he found the stomach 

 loaded with minced sea-weed. 



(2) For the purposes of zoology the expression * palatine teeth' serves in general sufficiently 

 to denote their existence, whether they be vomerine as in the Batrachia or pterygoid as in the 

 Saurians ; it is in this sense doubtless that the learned authors of the Erpetologie Generals, 

 describe the teeth of the Iguana and other Lacertians as being situated on the ' os palatines.' 



R 2 



