244 W. K. GREGORY HOMOLOGY OF LACRIMAL AND AL1SPHENOID 



The evidence is too detailed to be presented adequately at this time 

 and will shortly be published in the American Journal of Morphology, 

 but in outline it is as follows: Some of the distinguishing features of 

 the mammalian alisphenoids are : that they are lateral to the basisphenoid 

 and pituitary fossa; they lie between the orbitosphenoids and the otic 

 capsule; they connect above with the parietals; they are largely in front 

 of the foramen for the mandibular branch of the fifth nerve and behind 

 the fissure which gives exit to nerves III, IV, V 1 , and VI. Further, the 

 temporal wings of the alisphenoid lie outside the roots of the fifth nerve ; 

 they also are external to the carotid foramina and postero-external to the 

 pterygoid processes. In Cynodonts there are a pair of elements in the 

 temporal region of the skull which are described and figured by both 

 Broom and Watson and which are homologized by them with the tem- 

 poral wings of the mammalian alisphenoids. These alisphenoids of 

 Cynodonts correspond with the mammalian alisphenoids in all the more 

 important topographic relations, so that their homology can hardly be 

 doubted. 



The alisphenoids of Cynodonts in turn appear to afford a perfect tran- 

 sition to those of typical reptiles. In all their relations to surrounding 

 bones and to foramina their essential agreement with the alisphenoids of 

 Tyrannosaurus, for example, can hardly be denied. For tljese reasons I 

 feel pretty confident that the elements commonly called alisphenoids in 

 Crocodiles and Dinosaurs are rightly so named, and that von Huene is 

 wrong in calling them orbitosphenoids. The true orbitosphenoids were, 

 I think, correctly named by Parker in the Crocodile. They lie immedi- 

 ately behind the ethmoid, below the frontals, and in front of the alisphe- 

 noids. In Tyrannosaurus they are continuous below with the presphenoid 

 and are, I think, incorrectly named presphenoid by Doctor von Huene. 



Pterygoid, Epipterygoid, and Alisphenoid 



Another side of this thorny subject is the question of the relations of 

 the pterygoid, epipterygoid, and alisphenoid. Broom 10 has ably defended 

 the view first expressed by Parker that the temporal wings of the alisphe- 

 noids have been derived from epipterygoids, like those of SpJienodoii. 

 and that the alisphenoid represents a portion of the primitive pterygo- 

 quadrate cartilage. In Sphenodon the alisphenoids, or epipterygoids, lie 

 immediately in front of the prootic foramen and below the parietals. 

 They differ from the alisphenoids of Dinosaurs chiefly in retaining their 



10 Observations on the development of the marsupial skull. Proc. Linn. Soc. New South 

 Wales, vol. 34, pp. 211-212. 



