478 



MANUAL OF ZOOLOGY. 



o 



between forty and fifty 

 femur and tibia 



acetabulum (fig. 209), the elongation and slenderness of form 

 of the ischium, and the slenderness of the pubes. The astra- 

 galus is like that of a bird, and in some cases appears to have 

 become anchylosed with the distal end of the tibia. The 

 metatarsal bones, however, remain distinct, and are not an- 

 chylosed with any of the 

 tarsalbones to forma "tarso- 

 metatarsus. 



The most familiar ex- 

 amples of the Dinosauria 

 are Megalosaurus and Igua- 

 nodon. 



Megalosaurus is a gigantic 

 Oolitic Reptile, which oc- 

 curs also in the Cretaceous 

 series (Weald Clay). Its 

 length has been estimated 

 at 



feet, the 



each measuring about three 

 feet in length. As the head 

 of the femur is set on nearly 

 at right angles with the 

 shaft, whilst all the long 

 bones contain large medul- 

 lary cavities, there can be no 

 doubt but that Megalosaurus 

 was terrestrial in its habits. 

 That it was carnivorous and 

 destructive in the highest 

 degree is shown by the 

 powerful, pointed, and tren- 



Fibula ; as " ' f 



Astragalus ; ca Calcaneum ; m Metatarsus. Cliant teettl. 



(After Huxley.) The f guano j on i s rnainly, 



if not exclusively, Cretaceous, being especially characteristic 

 of the great delta-deposit of the Wealden. The length of the 

 Iguanodon has been estimated as being probably from fifty to 

 sixty feet, and from the close resemblance of its teeth to those 

 of the living Iguanas, there is little doubt that it was herbivo- 

 rous and not carnivorous. The femur of a large Iguanodon 

 measures from four to five feet in length, with a circumference 

 of twenty-two inches in its smallest part. From the dispro- 

 portionately small size of the fore-limbs, and from the occur- 

 rence of pairs of gigantic three-toed footsteps in the same beds, 

 it has been concluded, with much probability, that Iguanodon. 



Fig. 209. Leg of Deinosatir. il Iliur 

 Ischium ; f Femur ; t Tibia ; 



