ARTICLE 11. 



ON THE HOMOLOGIES OF THE POSTERIOR CRANIAL ARCHES 



IN THE REPTILIA. 



BY E. D. COPE. 



Read before the American Philosophical Society, February 5, 1892. 



At the meeting of the American Association for the Advancement of Science, 

 held in Troy, IN. Y., in 1870, 1 presented the result of my studies of the arches which 

 distinguish the posterior part of the ci'anium in the Vertebrata, and especially in the 

 Reptilia. Three arches were considered, which were named, commencing with the 

 inferior in position : the quadrat ojugal, the zygomatic and the parietoquadrate. Of 

 these the only arch recognized as occurring in the Mammalia was the zygomatic* 

 In the determination of this arch I followed Cuvier,f and for the following reason. 

 It was supposed that the quadrate bone represented one of the ossicula auditus. As 

 this element in the Mammalia is intracranial, and does not give support to an arch, 

 the zygomatic arch of that class could not be homologous with the ai'ch which it (the 

 quadrate) supports in the Reptilia (the quadratojugal). The zygomatic arch of the 

 latter class would be, on the contrary, that one which originates at the proximal 

 extremity of the quadrate, which would remain on the supposed withdrawal of the 

 latter within the skull as one of ossicula auditus. 



Prof Peters has, however, shown that the quadrate bone is probably not one 

 of the ossicula auditus, and he is followed by Dollo, Albrecht and others. In a study 

 of the osteology of the Permian reptile, Diopeus leptocepJialus Cope, J I came to the 

 conclusion that the quadratojugal arch of that reptile is the zygomatic arch of the 



* Proceedings Amer. Assoc. Adv. Sci., XIX, 1870, p. 197. 

 t Ossemens Fossiles, X, Ed. 1836, 14. 



:j: Clepaydrops leptoeephalus Cope. Proceeds. Amer. Philos. Soc, 1884, pp. 30-42. Diopeus, gen. nov., described 

 on a later page. 



