145 



properly being and to the succeeding vtrtebrm. The tpinoui proemti an it mag, com- 

 pressed, very gradually increase in length to the hue of the tail, and after the eighth caudal 

 vertebra begin M gradually to diminish, and finally disappear at the forty-first caudal vertebra. 

 In moat of the caudal vertebra- there may be observed a transverse line, as if the anterior 

 third pan of the centrum had remained in the state of an qiiphysis : it is at this line that 

 the vertebra breaks when a portion of the tail is voluntarily detached. The epiphysial rani- 

 lag* beenaau the nidus or centre of development of the cartilaginous or nbro-oartilpmm< 

 axis of the reproduced tail. To the ordinary scapular arch, consisting of scapula and coracoid, 

 there are here added clavicles and a long T-*haped epistenium. 



HmtttriaH. 

 067. The skeleton of an Iguana. 



The fontanelle or foramen in the middle of the coronal suture is well shown in this speci- 

 men. There are twenty -nine teeth in each upper jaw, and the length of this range is I J 

 inch. Twenty vertebra*, beginning at the fifth cervical, bear moveable ribs, the fifth to the 

 eleventh of which are articulated to the sternum. There are 2 sacral vertebra and 68 caudal 

 vertebne. 



Presented by Samuel SMMury, Esq. 



It was by their comparison with this skeleton, that the nature of the fossil teeth, 

 which had been found by Dr. Mantell in the Wealden strata of Sussex, and to which 

 Mr. Conybearc afterwards suggested the application of the name of Igtumodon, was 

 determined. Dr. Mantell, in his original communication to the Royal Society on the 

 subject, write* : " Among the specimens lately collected, some, however, were so 

 perfect, that I resolved to avail myself of the obliging offer of Mr. Clift (to whose 

 kindness and liberality I hold myself particularly indebted) to assist me in comparing 

 the fossil teeth with those of the recent Laccrta? in the Museum of the Royal College of 

 Surgeons. The result of this examination proved highly satisfactory, for in an Iguana 

 which Mr. Stutchbury had prepared to present to the College, we discovered teeth 

 possessing the form and structure of the fossil specimens." Philosophical Transac- 

 tions, 1625, p. 180. It is due, however, to Cuvier to state, that he had previously 

 suggested to Dr. Mantell that the fossil teeth from the Wealden which afterwards 

 bore the name of lytumodo* probably belonged to a herbivorous reptile. 



668. An abdominal vertebra of an Iguana. 



The centrum has the same general form as in the Farmnu ; bat its under surface has a 

 longitudinal depression on each side. The articular diapophysi* is smaller, the neural spine 

 higher ; but the chief distinction is seen in the presence of two small accessory lygapophyses 







