702 



ON SOME DINOSAURIAN REMAINS. 



individual ; their general facies, also, and the character of the osseous 

 tissues leave no doubt on my mind that they are parts of one skeleton. 

 From the same locality Mr. A. Leeds has also obtained many frag- 

 ments of large, thin, flat, bony plates, which cannot be referred to 

 any part of the endoskeleton and which doubtless represent a dermal 

 armour. Two of these shields, which have been reconstructed by 

 accurately placing together their fragments, show that their ori- 

 ginal dimensions were very considerable, the present breadth of 

 one being not less than 50 centim., and that of another about 80 

 centim. It has not yet been possible to reconstruct them so com- 

 pletely as to show their original contour. They are formed of 

 two thin tables with an intermediate diploe. The free surface of 

 one table is smooth and mostly of finer grain than the other, which is 

 usually impressed by long pits and furrows, and these, as also the finer 

 grain of the bone, show a radial arrangement starting from the 

 stoutest part of the plate, which rises as a low hummock above the 

 general level of that which I regard as the upper or outer surface. 

 This, which presumably represents the centre of ossification of the 

 plate, imparts a stoutness in one jnate of 3 centim., thinning out 

 towards the periphery to less than the thickness of a playing-card. 

 Perhaps this has been reduced by pressure. A few fragments pre- 

 serve a natural edge ; this has the form of a slightly swollen lip, bounded 

 towards the expansion of the plate by a submarginal groove, a con- 

 struction which suggests that adjoining plates may have been linked 

 together by intercalated flexible integument. 



The evident close affinity between Omosaurus and Stegosaurus 

 made it very probable that as the former possessed dermal spines it 

 would likewise be provided with tegumental plates ; I am therefore 

 disposed to associate with the other skeletal remains the plates in 

 Mr. Leeds's collection. Should this association be confirmed by new 

 discoveries, the question may arise, Does not the association rather 

 suggest that the remains should with greater justice be referred to 

 Stegosaurus than to Omosaurus? 



The Dinosaur they represent has, however, in its femur a distinct 

 inner trochanter ; this also is presentin the type of Omosaurus armatus ; 

 while it is stated that there is no evidence of its presence in 

 Stegosaurus. Should this difference be confirmed, it appears decisive 

 against the generic identity of these two Dinosaurs ; but for the 

 moment reservation is necessary upon this subject. 



Up to the present time the reptilian fauna of the Kimmeridge Clay 

 has been chiefly distinguished by the abundance of Ichthyopterygia and 

 Sauropterygia, for the numbers of its Ichthyosauri, its Plesiosauri, 

 and its Pliosauri in their many and distinctive modifications, not 

 less than for the numbers of its Crocodilians, the Teleosauri and 

 Steneosauri. 



Evidence is now accumulating that the Dinosaurian group was also 

 well represented, and this not by one but by several of its subgroups : — 

 (a) The Ornithopoda by Iguanodon Prestwichii ; (b) the Sauropoda 

 by Orniihopsis or a nearly allied form ; (c) the Stegosauria by Omo- 

 saurus armatus and Omosaurus durobrivensis. 



