30 FOSSIL REPTILES OF DORSET. 



PLIOSAURUS PORTLANDICUS, Owen. 



Sir Eichard Owen founded this species upon a femur, together 

 with other bones of the paddle, obtained from the Portland stone, 

 Portland, which is higher up in the series than the bed from which 

 the two former were procured. It is the first and only evidence 

 of the genus in so high an horizon. The femur has the usual 

 plesiosauroid character ; at the distal end is a row of two bones, 

 representing the fibula and tibia and a depression in the suture, 

 indicative of a third bone. 



PLIOSAURUS GAMMA, Owen. 



From the Oxford Clay, near Weymouth. Named by Sir R. Owen, 

 from a series of vertebrae cervical, dorsal, and caudal. 



The cervicals are extremely short, being only 1'20 inches in 

 length, 3'05 inches in breadth, and 2 '60 inches in height. They 

 differ from the rest of this genus in the apparent straightness of 

 the lower edge, caused by the very low position of the cicatrices, 

 which are triple, the middle one deeply excavated ; the articulating 

 surfaces are gently concave and rounded at the edges. There 

 are a few vertebrae of this species in the cases of the British 

 Museum. 



ORDER PTEROSAURIA, Owen. 



This Order comprises a remarkable family of flying reptiles, which 

 combines many peculiarities in their extraordinary and exceptional 

 structure. The centra of the vertebrae are concave in front, the 

 sternum keeled ; teeth implanted in distinct sockets, absent 

 or partially so in some genera, in which case the jaws appear 

 to have had a horny sheath like a bird ; the eye furnished with 

 sclerotic plates. The apparatus for flight was in some respects 

 similar to that of the Bat. Impressions of the sheets of skin have 

 been preserved, which its long strong fifth finger supported, but 

 no trace of hair or protecting feathers. Most of the bones are 

 hollow and capable of being filled with air for buoyancy. The 

 sacrum is formed of from three to six anchylosed vertebrae. 

 Pterosaurians are exclusively Mesozoic, ranging from the Lower 

 Lias to the Middle Chalk. 



