242 W. K. GREGORY HOMOLOGY OF LACRIMAL AND ALISPHENOID 



In. his paper of 1910, in which these views are expressed, Gaupp bases 

 his- conclusions entirely on the morphology of recent reptiles, especially 

 the lizards. The lizards on account of their streptostylic quadrate are be- 

 lieved by him to represent ancestral mammalian conditions in many parts 

 of the skull. 



What is the paleontological evidence in these questions of homology? 



In the Permian Cotylosaurs the lacrimal ( Gaupp' s adlaerimal) instead 

 of being vestigial, as in lizards, is a large bone that shows no signs of 

 being crowded out by the prefrontal. In Labidosaurus, for example, Pro- 

 fessor Williston 3 describes the lacrimals as lying in the anterior border of 

 the orbits (of which border they form the greater part), thence extending 

 forward, parallel to the maxillaries, to the anterior nares. The lacrimals 

 are equally large 4 in Seymouria, Limnoscelis, Captorliinus, Yaranosaurus, 

 and other genera. 



In the lowest members of the mammal-like series, namely, the Thero- 

 eephalia. 5 the lacrimal has been crowded away from the anterior nares by 

 the upgrowth of the maxillary, so that it has lost its anterior extension 

 and has begun to look like a mammalian lacrimal. In the higher Therap- 

 sida or Cynodontia 6 the lacrimal is a prominent bone on the anterior bor- 

 der of the orbit, which articulates with the jugal, maxillary, nasal, and 

 prefrontal. In Diademodon. according to Watson, 7 the lacrimal is 

 pierced by a lacrimal foramen and forms a part of the floor of the orbit. 



Hence Gaupp's views regarding the lacrimal receive no support what- 

 ever from the Cynodonts. On the contrary, if the Cynodonts are nearer 

 to the mammals than the lizards are. as there is good reason to believe, 

 then we must assume that in lizards and Sphenodon the prefrontal has 

 merely usurped the place of the true lacrimal, which has been crowded 

 out and become vestigial. 



Alisphenoid and OrbitospheNoid 



Gaupp has also raised an important question as to the homology of the 

 reptilian alisphenoid, denying that it is homologous with the true alis- 

 phenoid of mammals. 8 



3 The skull of Labidosaurus. Amer. Jour. Anat.. vol. 10. 1910. p. 73. 



4 See the figures in Williston's American Permian Vertebrates. Cniv. Chicago Press. 

 1911. 



5 See Broom : A comparison of the Permian reptiles of North America with those of 

 South Africa. Bull. Amer. Mus. Nat. Hist., vol. 28. 1910. pp. 204-213. 



6 See Broom : On the structure of the skull in the Cynodont reptiles. Proc. Zool. Soc. 

 1911, pp. 896-915. 



7 The skull of Diademodon. with notes on those of some other Cynodonts. Ann. and 

 Mag. Nat. Hist.. (8), vol. viii. 1911. p. 311. 



8 uber die Ala temporalis des Siiugeschiidcls und die Regio Orbitalis einiger anderer 

 Wirbeltierschiidel. Merkel und Bonnets Anat. Heft lxi 1 19 Bd.. Heft 1). 1902, pp. 221- 

 222. 



