AMERICAN LABYRINTHODONTIDM 601 



The palatine foramina are much shorter than those shown in 

 Broili's restoration of Eryops. They are separated by the parasphe- 

 noid and prevomers. The infratemporal foramina are long and 

 narrow. The internal nares are large, rounded posteriorly and 

 pointed anteriorly, and are widely sseparated from the palatine 

 foramina. As the premaxillaries are somewhat imperfect anteriorily, 

 the shape of the premaxillary foramina cannot be definitely deter- 

 mined. They do not penetrate the roof of the skull. 



Base of skull. — The foramen magnum is remarkable because of 

 its small size. In none of the specimens in the collection does its 

 greatest diameter exceed 2 cm . As it is distorted by pressure, in all 

 of the skulls, it is impossible to determine its exact shape, but it 

 seems to have been oval, with its transverse diameter the greater. 



The exoccipitals form the margins of the foramen, except above, 

 where the supraoccipitals project downward between them. In the 

 floor of the skull the exoccipitals are thick, and co-ossified with each 

 other and with the parasphenoid. The condylar processes are 

 short and strong, and the articular surfaces are concave. A short, 

 strong upward projection from just in front of the condyles forms 

 the lateral boundary of the foramen magnum and broadens to a head 

 above, articulating firmly with the supraoccipitals. A long, slender 

 lateral process, homologous with the opisthotic (paroccipital, Baur) 

 of reptiles, passes outward to articulate with the epiotic (paroccipital 

 plate, Baur) at its outer end. Between this process and the bones 

 •of the roof of the skull there is an elongate oval foramen, which is 

 homologous with the posttemporal foramen of the Reptilia. 



The posterior wing of the pterygoid, where it turns upward to 

 articulate with the quadrate, forms a considerable part of the base 

 of the skull. The quadrate extends from the cotylus to the auditory 

 slit, showing as a long, narrow strip in the base of the skull. Along 

 its entire upper edge it articulates firmly with the prosquamosal, 

 along its lower edge with the pterygoid. The quadratojugal meets 

 it at its lower outer corner. The surface for articulation with the 

 mandible is somewhat saddle-shaped, and is formed entirely by the 

 quadrate. 



Mandible. — The sutures in the mandible of Eryops have never 

 before been determined, but in all of the specimens in Walker Museum 



