256 Prof. 0. C. Marsh — J!^eio Jurassic Dinosaurs. 



margin of the pterygoid is united the strong, curved, transverse 

 bone, whicli projects downward below the border of the upper jaws, 

 as shown in Figure 1, t. 



There is a very short, thin, columella, which below is closely 

 united to the pterygoid by suture, and above fits into a small 

 depression of the post-frontal. 



The palatine bones are well developed and, after joining the 

 pterygoids, extend forward to the union with the vomers. The 

 latter are apparently of moderate size. 



The pre-sphenoid is well developed, and has a long pointed 

 anterior extremity. 



The whole palate is remarkably open, and the principal bones 

 composing it stand nearly vertical, as in the Sauropoda. 



The Brain. — The brain in Ceratosaiirus was of medium size, but 

 comparatively much larger than in the herbivorous Dinosaurs. It 

 was quite elongate, and situated somewhat obliquely in the cranium, 

 the posterior end being inclined downward. The position of the 

 brain in the skull, and its relative size, is shown in Fig. 3. 



The foramen magnum is small. The cerebellum was of moderate 

 size. The optic lobes were well developed, and proportionally 

 larger than the hemispheres. The olfactory lobes were large, and 

 expanded. The pituitary body appears to have been very large. 



The Lower Jaws. — The lower jaws of Ceratosaurus are large 

 and powerful, especially in tlie posterior part. In front, the rami 

 are much compressed, and they were joined together by cartilage 

 only, as in all Dinosaurs. There is a large foramen in the jaw, 

 similar to that in the crocodile, as shown in Fig. 1,/. The dentary 

 bone extends back to the middle of this foramen. The splenial is 

 large, extending from the foramen forward to the symphysial sur- 

 face, and forming in this region a border to the upper margin of the 

 dentary. There were fifteen teeth in each ramus, similar in form to 

 those of the upper jaws. 



A peculiar dentary bone, recently found, and here referred to 

 Labrosaurus, is edentulous in front, and the posterior portion is 

 much decurved. The teeth are more triangular than in the other 

 genera of this order. The species it represents may be "called 

 Lahrosaurus ferox. 



The VERTEBRiE. — The cervical vertebrae of Ceratosaurus differ in 

 type from those in any other known Keptiles. With the excejDtion 

 of the atlas, all are strongly opisthocoelian, the cup on the posterior 

 end of each centrum being unusually deep. In place of an equally 

 developed ball on the anterior end, there is a perfectly flat surface. 

 The size of the latter is such that it can only be inserted a short 

 distance in the adjoining cup, and this distance is accurately marked 

 on the centrum by a narrow articular border, just back of the flat 

 anterior face. This peculiar articulation leaves more than three- 

 fourths of the cup unoccupied by the succeeding vertebra, forming, 

 apparently, a weak joint. This feature is shown in Fig. 4. 



The discovery of this new form of vertebra shows that the terms 

 opisthocoelian and procoelian, in genei'al use to describe the centra 



? 



