54. PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



(fig. 8), is, I suggest, neither " the apophysial lever of the fibula," nor 

 " the calcaneum," nor yet " a detached olecranon," but it is the fibula 



Pig. 8. — End of Femur, Epipodial and Tarsal Bones of Pliosaurus 

 portlandicus, Owen. (From a plate in the 'Fossil Keptilia.') 



T, the tibia=66, tibia, Ow. ; 67, the intermedium = fibula, Ow. ; 67', the fibula= 

 fabella, Ow.; t, os tibiale ; c l , c 2 , ossa centralia. 



itself; and the ossicle marked 67 in the same figure is not the fibula, 

 as its number would imply, but it is the intermedium. In the dia- 

 gram fig. 7 (copied from fig. 3 in pi. xli. vol. xxv. Quart. Journ. 

 Geol. Soc. 1870), which represents the paddle of Plesiosaurus 

 Manseli, the letter T marks the tibia ( = 66 Owen), i denotes 

 the intermedium ( = 67 Owen), and F the fibula ( = 67' Owen). I 

 imagine that the identity of these three elements in the epipodial 

 segment of the above two paddles is unquestionable, and also that 

 their identity with the three epipodial elements in the paddle of 

 Sauranodon figured by 0. C. Marsh is beyond doubt (fig. 9). I 

 think also that the homology of the two laterally placed ossicles in 

 the epipodium of Sauranodon with the two similarly situated ossicles 

 in the epipodium of Ichthyosaurus (fig. 10) cannot be disputed. But 

 these latter are by general consent the homologues of the tibia and 

 fibula of higher vertebrates. It follows, therefore, that the lateral 

 ossicles in the epipodium of Pliosaurus portlandicus (66, 67') and 

 in that of Plesiosaurus Manseli (T, F) are also the tibia and fibula. 

 Now the middle ossicle in the epipodium of Sauranodon has been 

 identified by 0. C. Marsh, rightly as I think, with the intermedium, 

 the opinion at which I had myself arrived with respect to the cor- 

 responding element in Plesiosaiwus Manseli, though noticing its 

 agreement with the ossicle which in Ichthyosaurus is intercalated 

 between the distal halves of the tibia and fibula. Here it has lost 



