WEALDEN FORMATIONS. 7 



The radius of the Iguanodon resembles that of Lizards — Iguana tuberculata, Monitor 

 niloticus, for example — in the larger and more definite extent of the proximal surface for 

 the ulna, than exists in the Crocodilia. But no living reptile — crocodilian, chelonian, or 

 lacertian — is armed like the extinct herbivorous Dinosaur. 



Of other examples in the animal kingdom of limbs with spinous weapons, the first 

 that suggested itself was the monotrematous reptile-like Mammals. But in both Orni- 



FlG. l. 



Sexual spines of fore-limbs ; or 'Hand-spurs,' Male of large S. Amer. Toad {Cystignathus fuscus). 



thorhynchus and Echidna they are limited to the hind limbs, and are attached to the 

 tarsus, not to the tibia. 



In the class of Birds are a few ' spur- winged ' species — Anser gambensis, Parrajacana, 

 Palamedea cornuta, Ifoplopterus, e.g. — in which the weapons are attached to the radial side 

 of the fore-limbs ; not, however, to the radius itself, but to the base of the metacarpus. 



My friend and colleague, Dr. Gimther, has kindly supplied me with the following 

 example of spines or spur-like weapons in an existing cold-blooded air-breather; but 

 it is a member of the Batrachian order. In Cystignathus fuscus a sharp, conical, horny 

 spine, figure 1, s, s, is supported by a bony core attached to the radial side of the meta- 

 carpal of the innermost or radial digit. 



Many species of Fish support and wield with effect formidable spinous weapons, forming 

 part of the pectoral fins, the homologues of the fore-limbs in Iguanodon and other 

 terrestrial Vertebrates. 



