FOSSIL REPTILES OF DORSET. 39 



These vacuities of the centra must have lightened the weight of the 

 spinal column and adapted the animal to an amphibious life. 



ORNITHOPSIS LEEDSII, LydekJcer.* 

 Ceteosaurus Immerocristatus, Hulke. 



Like the Iguanodon and Megalosaurus, all the articulations of 

 the limb bones allow gliding movement ; they have no intervening 

 cartilaginous bond as with Ichthyosaurus and other Enaliosaurians, 

 adapting them to be both flexible and powerful instruments for 

 swimming, but suited for terrestrial progression. The free movement 

 of the head of the femur in the hip-cup and the large claws 

 strengthen this view. A humerus of this genus from the Kim- 

 meridge Clay of Weymouth is described by Mr. Hulke in vol. xxx. 

 of the " Quarterly Journal of the Geological Society," p. 16, with 

 a plate. The articular surfaces of both extremities are wanting ; 

 without these the length is four feet six inches (when perfect it 

 must have been five feet three inches). Its girth at the middle of 

 the shaft is one foot nine inches. 



ORNITHOPSIS MANSELII, Lydekker. 



Iscliyrosaurus Manselii^ Hulke. 



Determined by Mr. Hulke > upon the evidence of a humerus I 

 found in the Kimmeridge Clays of Kimmeridge, and presented to 

 the British Museum. Its length is two feet seven inches, and girth 

 near the middle of the shaft one foot one inch, at its proximal end, 

 which joins the shoulder, two feet. It has no medullary cavity. 

 Mr. Hulke tells me he thinks it probable that both this and the 

 preceding will be found to be identical with Ornithopsis, found in 

 the Wealden of the Isle of Wight and in the Kimmeridge Clay 

 near Peterborough. Its correspondence with the American fossil 

 Brontosaurus of 0. E. Marsh may ultimately prove Ornithopsis 

 also to be a synonym. 



* For the grounds on which this and the next species are now referred to 

 Ornithopsis consult Mr. Lydekker's recently published paper and the 

 "Quarterly Journal Geological Society," vol. xliv., part 1, p. 46, 1 Feb.* 

 1888. 



