THE UPPER TRIASSIC OF WESTERN TEXAS. 33 



wall of the brain-case, but it seems probable that all of these, except possibly a distinct 

 epiotic, had such an arrangement and that the quadrate runs forward on the brain-case 

 nearly the full length of the opisthotic and joined the prootic in front and perhaps the 

 squamosal above. The quadratojugal did not send any process forward on the anterior 

 or lower edge of the quadrate, as in the Crocodilia. 



In figure 8 is given a sketch of the condition of the skull as originally imagined by 

 the author and as suggested to him by both Doctor F. v. Huene and Doctor D. M. S. 

 Watson. Reasons have been given above why this suggestion must be rejected, but 

 there is much weight in the objection offered by Doctor Watson that in the phytosauroid 

 reptiles the basicranial region is never so far below the quadrate. Future discoveries 

 may show that the alternative restoration is correct and that Desmatosuchus must be 

 placed among the Parasuchia. At present the restoration and explanation here given 

 seem to the author the only ones possible. 



Description of the endocranial cast (plate 6, figs. A, B, c). — A description and 

 discussion of the endocranial cast of Desmatosuchus has already been published 1 and 

 only a portion of it is repeated here. 



"The cranial cavity of Desmatosuchus was completely cleared out, leaving the surface of the 

 hone in good condition with all the pits and foramina clearly marked. As may be seen in the fig- 

 ures, the cast as finally secured shows the general form and proportions of the brain cavity and the 

 positions of the main outlets. The anterior wall of the cavity was entirely cartilaginous or mem- 

 branous, and as this jxjrtion was not preserved in the fossil the opening was stopped with plastic 

 clay which is easily detected in the figures. For this reason, the form of the olfactory tract and of 

 the pituitary body is not completely shown. 



"The olfactory tract was evidently large, as in most of the primitive forms, and extended well 

 forward directly beneath the upper wall of the skull. The cerebral portion was relatively small, 

 scarcely any swelling Ix-ing revealed in this part of the cast except at the posterior end of the 

 prosencephalic region. The anterior-lower part of this region was enclosed by the ali-, orbitosphenoid 

 bones, ami the approximation of the hones of the two sides forms notches in two places which indi- 

 cate the points of escape of the nerves which supplied the eye. No indication of the origin of the 

 II, III, or IV pair of nerves is shown on the cast, and no outlets except the notches mentioned. 



"It is impossible in the cast to distinguish between the diencephalic and the mesencephalic 

 regions of the brain, but the area occupied by these two is marked by a slight but distinct depres- 

 sion, which is outlined by definite elevations, the posterior one amounting to a low, sharp ridge. 

 From this depression rise the processes, above and below, which may be referred to in general 

 terms as the epiphysis and the pituitary body. 



"The upper process is complex and is, perhaps, composed of two parts. Just posterior to the 

 edge of the prosencephalic portion there are two protuberances which mark the position of a pair 

 of deep pits in the upper wall of the brain-case. In cleaning the skull it was impossible to be cer- 

 tain that the bottom of these cavities had been reached, but it seemed probable that it had. With 

 the aid of a dentist's mouth-mirror and fine curved awls the pyrite filling was picked out until it 

 seemed that the bottom had been reached, but because of the inaccessibility of the cavities and their 

 small diameter it is possible that the cavities may have been deeper and even that they may be 

 the entrances to foramina. Cope, in describing the endocranial casts of a Phytosaur, Belodon, 

 and of a cotylosaurian reptile, Diadectes, speaks of the 'lateral processes of the epiphysis' and in 

 describing the skull of Belodon sjH'aks of the process as lying in a 'large canal which enters the 

 posterior part of the orbit.' To this canal he gave the name of the orbitopineal process on the 

 casts. The function of this canal he was unable to determine, but suggests that it carried a nerve 

 or blood-vessel. 2 In his earlier papers he was inclined to the belief that Diadectes was blind because 

 he could find no outlet for the optic nerve and because the structure of the animal suggested that 



'('use. El C, On :m Endocranial ( ':ist from u Reptile, Deamatoguchu* rpurentu, from the Upper Triassic of 

 western Texas, .Jounce! of Comparative Neurology, vol. 33, No. 2, p. 133, 1921. 



2 Dr. H. L Moodie, in conversation with the author, baa suggested that these processes may indicate a portion 

 of the eOUne of the ductus eucloh luphuticus. 



