Cope.] ^0± [ 0ct . 16i 



On the Structure of the Brain and Auditory Apparatus of a Theromorphous 

 Reptile of the Permian Epoch. By E. D. Cope. 



(Read before the American Philosophical Society, October 16, 1SS5.) 



The following observations are made on a part of a skull of one of the 

 Diadectidse (Pelycosauria with transverse molar teeth*), which is accom- 

 panied by several vertebrae and other fragments of the skeleton, of a 

 single individual of undetermined species. A few characters are derived 

 from skulls of two allied species, Diadectes phaseolinus and Empedias 

 molaris Cope, which, like the first named specimen, were derived from the 

 Permian formation of Texas. A cast of the brain chamber was obtained, 

 thanks to the skill of my assistant, Mr. Geismar, first in the elastic mate- 

 rial patented by Bendernagel & Co., of Philadelphia, for the manufacture 

 of printers inking rolls ; and afterwards in plaster of Paris, in a mould 

 made from the elastic cast. 



The brain case in the Diadectidre differs from that of the Clepsydropidae 

 much as that of the Varamidse differ from those of other Lacertilia. That 

 is, it is continued between the orbits, so as to enclose the olfactory lobes 

 of the brain within osseous walls. These w r alls are thin ; especially at the 

 interorbital region, and in the specimen the anterior extremity is so far 

 imperfect as to leave the form of the anterior fundus in doubt. 



The brain in reptiles, as is well known, does not fill tightly the cranial 

 chamber as is the case with the Mammalia, there being a wadding of con- 

 nective tissue, with interspaces filled with lymph and fat, between it and 

 the cranial walls. In the present species the postfrontal part of the 

 cranium is so contracted that there could have been but little space of this 

 kind, and the superior walls are clearly impressed by the surfaces of the 

 middle brain and the cerebellum. The form of the inferior surface of the 

 brain posterior to the fifth pair of nerves cannot be determined from the 

 specimen examined, owing to the absence of the basioccipital and basi- 

 sphenoid bones. 



The conformation of the cranial walls requires preliminary notice. In 

 the first place the vestibule of the ear can only have been separated from 

 the brain by a membranous septum, as is the case in the Protonopsis hor- 

 rida\ (Menopoma). In clearing out the matrix no trace of osseous lamina 

 could be detected on either side, and the edges of the huge foramen thus 

 produced are entire, and present no broken edges. Anterior to the vesti- 

 bule, the prootic bone has a small extension, terminating in a vertical 

 border. In front of this is the huge vertical foramen through which issues 

 the trigeminus nerve, which is even larger than that found in the Testudi- 

 nata and Crocodilidai. The anterior border of this foramen is formed by 



* For a definition of this family and the included genera, see Proceedings of 

 the American Philosophical Society, 18.S0, p. 45. 



fSee Journal Academy Philadelphia, 1SU6, p. 105, where the characters of the 

 skull in the Urodela are pointed out. 



