208 
PROFESSOR H. G. SEELEY ON THE STRUCTURE, ORGANIZATION, 
the base of the fang when the tooth became anchylosed. I am inclined to regard the 
attachment of the teeth as having more in common with Serpents and certain Lizards 
than any other group of existing animals ; but the resemblance cannot be accounted 
one of affinity. And the question arises whether the sub-dental cavities are not to 
be interpreted as a stage in the history of the formation of the socket for alveolar 
teeth, which became developed in a later period of time. If there had been sufficient 
evidence to establish this interpretation, it would have tended to make Protorosaurus 
comparable with some Ornithosaurs from Solenliofen, to which resemblances may be 
seen in the general structure of the skull and conformation of the palatal bones, 
though no Ornithosaur has teeth on the bones of the palate. 
The vertebral column .—-The atlas is very short and not anchylosed to the axis. 
There are about 7 cervical vertebrae : 16 dorsal; two or three sacral; and an unknown, 
but large, number in the tail. These numbers throw no light on the affinities of the 
fossil. The elongation of the cervical vertebrae, as von Meyer pointed out, is better 
paralleled among Ornithosaurs than any other group. The strongly developed neural 
spine is not found in all members of this group, but is sufficiently characteristic. 
Yon Meyer’s figures appear to show that the vertebrae have the articular ends of the 
centrum slightly concave ; and therefore it is probable that if the opisthocoelous 
condition which the type appears to show is not delusive the form of the articulation 
is not constant. I do not know of any Ornithosaur which has a like antero-posterior 
elongation of the neural spine. The cervical ribs are Ornithosaurian. The dorsal 
vertebrae are remarkable for the rounded base and depth of the centrum, which 
supports a large neural arch with vertical truncated neural spine. This form of 
vertebra approximates rather to the Crocodilian than the Lacertilian type, but is 
Fig. 3. 
Fourth cervical vertebra of Protorosaurus Speneri. 
better matched among existing Birds with amphiccelous vertebrae, Pterodactyles, 
Dinosaurs, and Nothosaurs, though it never has anything like a neural platform; and 
there is no certain evidence of any ribs having more than one articular head, though 
the articulation of the rib was quite as high in lateral position as among Crocodiles. 
On the whole, the Ornithosaur comes closest, though Rhynchosaurus , in the form of 
the centrum, is not dissimilar. There is no approximation to the massive neural arch 
of Nothosaurus, and the centrum is more elongated than in that genus. 
The sacrum presents no peculiarities ; and, although only two pairs of strong sacral 
ribs were developed to support the ilium, that bone appears to have been sufficiently 
