34 NEW REPTILES AND STEGOCEPHALIANS FROM 



it was burrowing in habit; as the parietal foramen is exceptionally large in this form, he was in- 

 clined to believe that the orbitopineal canal might have carried a nerve from the large, probably 

 functional eye which occupied the parietal foramen, which in part supplied the necessary vision. 

 It is impossible to tell whether such a canal existed in Desmatosuchus, but if it was present it was 

 very small, and the author of this paper is inclined to believe that it did not exist. Moreover, 

 there is a decided difference in the endocranial casts in this region. In Belodon and Diadectes the 

 processes are large and rise from the sides of the epiphysis, in Desmalosuchus they are small and are 

 entirely anterior to the epiphysis. It is possible that if a true cast of the brain could be obtained 

 the origin of the processes might be found to be the same in all, but as the casts were all made from 

 empty cavities a similar origin should be apparent. 



"The epiphysis is very different in form. In Belodon and Diadectes theie is a strong posterior 

 process, and Cope describes the epiphysis of the former as 'subquadrate.' The orbitopineal pioccss 

 extends either directly outward from the side, Diadectes, or outward and forward, Belodon. In 

 Desmatosuchus the epiphysis is erect and narrow antero-posteriorly with no posterior process. In 

 both Belodon and Desmatosuchus the processes referred to as the epiphysis are casts of a deep pit 

 on the under side of the skull in the exact position of the pineal foramen in other reptiles, but in 

 neither of these is the roof perforated. In looking up this matter the author has found that much 

 uncertainty exists as to the exact character of this process in the brain; it is known that both the 

 epiphysis and the paraphysis may reach large size and that either one may terminate in a func- 

 tional eye; at least, either one may carry organs which possess the histological structures of the 

 retina and the crystalline lens. In some forms there has also been found a third evagination of the 

 brain, posterior to the epiphysis, called the pineal organ, which has a similar histological structure. 

 Wilder, in his History of the Human Body, states that it is the paraphysis which was developed in the 

 extinct Stegocephalia and filled the parietal foramen, and the epiphysis which was developed in 

 the reptiles, birds, and mammals. On the other hand, it is known that the epiphysis is not devel- 

 oped in the modern alligator. The term epiphysis is used in this paper only in a general sense and 

 without knowledge of its true nature. 



' ' On the lower side of the diencephalic region of the cast is the second process ; this represents 

 the combined infundibulum and the saccus vasculosus, or the pituitary body. Only the posterior 

 and lower borders are shown, for the anterior part was enclosed by the cartilaginous anterior wall 

 of the skull which was lost in fossilization. The process extended directly downward by a narrow 

 neck which passed through a narrow notch formed by the approximation of the alisphenoid bones 

 at their lower borders. Its posterior face lay against the basisphenoid bone, not penetrating it, 

 and its lower surface in an excavation on the upper surface of the posterior part of the parasphenoid. 

 The lower part of the process was enlarged and the posterior face, at least, extended backward at 

 a sharp angle. The lower end terminates in a bifurcate extension which is formed by the casts of 

 the beginnings of two foramina which open outwardly and downward in an excavation on the upper 

 surface of the parasphenoid. These foramina continue and terminate in deep grooves on the side 

 of the basisphenoid. On the posterior face of the process are two small prominences which mark 

 the position of two foramina on the lower face of the basisphenoid, evidently the openings for the 

 internal carotid arteries. 



"The posterior part of the depressed area mentioned above must also include the meson- 

 cephalic portion of the brain, but there is nothing to mark the presence of either optic lobes or optic 

 thalami. This does not, however, suggest either their absence or relatively small size, for if a cast 

 were made of the cranial cavity of Sphenodon or of an alligator no evidence of these structures 

 would appear, though they are of large size. 



' ' Posterior to the depressed area tho whole cast is curved sharply downward and then straight- 

 ened out horizontally in the metencephalic region. On the lower edges of the anterior part of this 

 region there are large prominences which mark the position of the large foramina for the passage 

 of the V pair of nerves. There is no indication in the cast of the division of this nerve into its 

 parts; this must have taken place external to the cranial wall. Within and a little posterior to 

 these prominences is indicated the position of a pair of small foramina in the floor of the skull, 

 evidently the outlets for the VI pair of nerves. Posterior to the V and at about the middle of the 

 posterior part of the cast, there are a pair of processes on each side, one almost directly above the 

 other. The upper pair are the casts of the otic cavities and mark approximately the position of 

 the VIII, and probably, also, the VII nerves, for these two nerves escape from the skull of the Croco- 



