518 



SCIENCE 



[N. S. Vol. XXVIII. No. 720 



Three pairs of bones forming the side walls 

 of the brain-ease have been identified by Dr. 

 Holland as the exoccipitals, the alisphenoids 

 and the orbitosphenoids. As to the exoccipi- 

 tals, he is right. Nothing whatever is said 

 by him about the prootics, although they are 

 among the most important and constant 

 bones of the reptilian skull. The fact is, 

 however, that the bones regarded by our au- 

 thor as the alisphenoids are in reality the 

 prootics, while his orbitosphenoids are the 

 alisphenoids. The orbitosphenoids are only 

 slightly developed and are thoroughly consoli- 

 dated with the alisphenoids. That the bones 

 called by Dr. Holland the orbitosphenoids 

 are in fact the alisphenoids is shown by the 

 presence of the optic foramina in front of 

 them. 



Dr. Holland has represented the supraoecip- 

 ital bone as occupying a small lozenge- 

 shaped area on the upper surface of the skull 

 and narrowing to a point right and left. 

 Now, in all reptiles this bone, by virtue of its 

 epiotic element, takes an essential part in 

 the formation of the internal ear, containing, 

 as it does, the posterior semicircular canal. 

 It must, therefore, come into contact with 

 the exoecipital and the prootic not far above 

 the fenestra ovalis. The three bones concerned 

 are, in the Pittsburg specimen and all others 

 known, thoroughly coossified and the sutures 

 are nearly effaced. However, the writer be- 

 lieves that the suture between the supra- 

 occipital and the exoecipital starts about 

 25 mm. above the fenestra ovalis and runs 

 outward and backward to a notch in the 

 hinder border of the posttemporal fossa. In 

 Dr. Holland's figure 5 this suture would start 

 from the suture ascending at the left of the 

 letters ex.o, at the upper border of the post- 

 frontal bone and run backward just below 

 these letters, and end under the bone sq. The 

 suture between the prootic (Dr. H.'s alisphen- 

 oid) and the parietal falls so low that it would 

 properly be hidden behind the postfrontal. 

 The line representing the hinder border of 

 the parietal in the supratemporal fossa is, in 

 that figure, directed too far to the rear as it 

 descends. The letters ex.o lie on the supra- 

 occipital. On the upper surface of the skull. 



the suture between the supraoccipital and the 

 exoecipital probably starts on the midline, as 

 represented by Dr. Holland's figure 4, and 

 runs outward to the notch already mentioned 

 and seen near the letters AS. The supra- 

 occipital is thus given the importance that it 

 has in the reptilian skull. 



Dr. Holland has correctly identified the 

 olfactory, the optic and the hypoglossal fora- 

 mina, likewise that giving entrance to the 

 internal carotid artery; as to the others, I 

 believe that he is in error. The foramen as- 

 signed by him to the oculomotor nerve is sit- 

 uated between the alisphenoid and the pro- 

 otic, which is just the place for the trigem- 

 inal nerve. Just below this there is, in the 

 Pittsburg specimen, a group of three small 

 foramina which are supposed by Dr. Holland 

 to have given entrance to the anterior branch 

 of the internal carotid. These foramina are 

 below the floor of the brain-case and almost 

 certainly opened into the pituitary fossa; and 

 probably they afforded exit to the ophthalmic 

 artery. 



As already indicated, that foramen which 

 Dr. Holland has identified as that for the 

 trigeminal nerve is regarded by myself as the 

 fenestra ovalis. It lies on the boundary be- 

 tween the prootic and the exoecipital, where 

 the fenestra ovalis is to be sought. It is a 

 trilobate opening, but in a specimen in the 

 IT. S. National Museum the anterior lobe is 

 cut off by a bridge of bone. Here probably 

 escaped the facial nerve. The base of the 

 stapes was no doubt placed in the remainder 

 of the opening. 



The foramen for the internal carotid artery 

 lies in the exoecipital near its anterior border. 

 Just behind this comes the foramen called by 

 Dr. Holland the fenestra ovalis. While not be- 

 lieving it to be this fenestra I can not, in the 

 present condition of the skull, say with 

 certainty what was its function. It seems 

 probable that here, as in some other reptiles, 

 the ninth nerve passed out through this fora- 

 men separately from the tenth nerve. The 

 latter certainly escaped through the foramen 

 marked by Dr. Holland with the Eoman nu- 

 meral IX. in his figures. 



In speaking of his supposed fenestra ovalis 



