34 ROY L. MOODIE 



It is worthy of note that the palatal elements in Diplocaulus 

 do not take part in the formation of the prolongation of the 

 dorsum of the skull and we get an idea of the primitive condition 

 of the skull of the Diplocaulidae from the circumscribed area of 

 the palatal elements which are restricted by the quadrates to the 

 anterior portion of the skull so that all of the elongation and expan- 

 sion has taken place in the dorsum. 



The palatal openings are all lateral in position. The internal 

 nares are the most anterior. They are small, oval and transverse 

 in position. They are bounded by the premaxillae, vomers 

 and palatines. The palatine foramina are large, oval openings 

 situated below the orbits on either side of the median line. Their 

 long axis is parallel to the axis of the skull. They are bounded 

 by the parasphenoid, transverse, vomers and palatines. The 

 infratemporal foramina lie anterior and somewhat medial to the 

 quadrates. The openings have a rounded triangular form and 

 are bordered by the transverse, the maxilla, the quadratojugal, 

 the quadrate and the pterygoids. Posterior to the quadrate there 

 is an elongate groove which is possibly homologous with the 

 quadrate foramen of the Pelycosaurian genus Dimetrodon, 

 of Sphenodon, Anaschisma and other stereospondylous forms. 

 Its function here seems to be for the attachment of the masseter 

 and temporalis muscles. It certainly has the position of the 

 quadrate foramen in other forms. Its elongation is due to 

 the backward growth of the epiotic horns. The other opening 

 marked es in fig. 6, is undoubtedly the external auditory meatus. 

 It represents in part the otic notch or ear slit of other Stegocephala 

 so well shown in Metoposaurus, Mastodonsaurus, and Archego- 

 saurus. Broili has called them the ' Ohrenschlitzgruben' and he 

 is undoubtedly right. 



The mandible of Diplocaulus magnicornis Cope is moderately 

 heavy, though comparatively slight when compared to the size 

 of the skull. The sutures on the mandible have been impossible 

 to determine, with the exception of those bounding the articular. 

 They show the articular to have been a triangular element. The 

 teeth of the mandible consist of about thirty-five to forty short 

 blunt cones. The form of tooth appears to be well adapted to 



