90 Dr Mantell on the Structure of the Iguanodon, 



ing discovery made but a few days previously by S. H. Beckles, Esq. 

 of St Leonard's. 



With much labour and skill, Mr Beckles had succeeded in extract- 

 ing from a block of Wealden sandstone lying on the Sussex coast, 

 and which was only visible at low water, the perfect radius and ulna 

 (bones of the fore-arm), and humerus (arm-bone), of a gigantic rep- 

 tile, which Dr Mantell pronounced to be a new species of Peloro- 

 saurus, and proposed to name Pelorosaurus Becklesii. The generic 

 identity and specific difference between this humerus and that of the 

 Pel. Conybeari, which was placed beside it, were pointed out, and 

 the remarkable modification of structure presented by the ulna was 

 explained. The arm- bone of the P. Conybeari is 54 inches long, 

 the corresponding bone of a Gavial or Gangetic Crocodile 18 feet 

 long, in Dr Grant's Museum, is but 11^ inches ; the humerus dis- 

 covered by Mr Beckles is 22^ inches in length, and the bones of 

 the fore-arm are 16 inches long. A portion of the scaly cuirass 

 which covered the limbs, and is composed of hexagonal plates, was 

 exhibited. 



The lecturer then took a rapid view of the other reptiles that 

 were contemporary with the Iguanodon, enumerating the Pterodac- 

 tyles or flying lizards, and several genera of Crocodilians and Che- 

 lonians. Examples of marine and fresh-water turtles are not un- 

 common in the Wealden deposits ; and the strata near Swanage 

 have furnished many beautiful specimens to the researches of Mr 

 Bowerbank. 



Of Fishes there are nearly forty known species in the Wealden, 

 which are chiefly referable to the Ganoid and Placoid orders. The 

 fishes most abundant in the rivers of the Iguanodon country were 

 two or three species of Lepidotus, — ganoids closely allied to the 

 Bony or Gar-Pike of America ; their teeth and scales are every- 

 where to be met with in the Tilgate strata. 



The Invertebrate Fauna comprised many genera of Insects, a 

 few Crustaceans, and numerous fresh-water Mollusca. The Insects 

 (for a knowledge of which we are mainly indebted to the scientific 

 acumen of the Bev. P. Brodie) amount to several hundred speci- 

 mens, comprising between thirty and forty families or genera, and 

 are referable for the most part to the orders Coleoptera, Orthop- 

 tera, Neuroptera, Hemiptera, and Biptera. Among them are 

 several kinds of beetles, dragon-flies, crickets, May-flies, and other 

 familiar forms which are closely allied to species that inhabit tempe- 

 rate climates. 



Mollusca. — The most numerous shells belong to the genera Cy- 

 clas and Paludina ; of the latter, which is a genus of fresh-water 

 .snails, there are a few species that abound in the Wealden clays 

 and Purbeck beds, and form extensive strata of shelly limestone, the 

 compact masses of which are susceptible of a good polish, and are 





