I20 AMPHIBIA AND PISCES OF THE PERMIAN OF NORTH AMERICA 



highest'in the"middle, possibly for the attachment of nuchal muscles. The 

 cranial table in front of this transverse rugosity and between the slightly 

 elevated lateral margins is flat or gently concave. 



"On the sides posteriorly there is a large cavity, with an angulated 

 slit-like opening at its bottom, forming a false temporal fenestra, which 

 doubtless is merely a greatly enlarged and closed otic notch.* It is bounded 

 above by the heavy overhanging lateral border of the cranial table. The 

 epiotic angles, produced into long horns, instead of ending freely, as in other 

 Stegocephala, turn directly downward to fuse with the quadrate below, 

 inclosing what would otherwise be a simple notch into a large fossa and 

 opening. Its whole exterior and outer surface is roughened like other parts 

 of the skull. The cavity thus inclosed extends angularly at its upper ante- 

 rior angle to within about 20 millimeters of the middle of the hind border 

 of the orbit and is smooth throughout. At its bottom there is a thin, flat, 

 angular plate, attached to the lower anterior inner side of each epiotic horn, 

 projecting upward and forward to an acute angle, leaving a narrow, slitlike 

 perforation above connected with another in front, reaching the lower part 

 of the cavity, angularly dilated at the upper anterior part. Close to the 

 anterior border of this plate, and near its upper angle. Is the projecting end 

 of the stapes, as shown in plate 17, fig. 3.t The upper margin of the perfo- 

 ration in front Is formed by a narrow descending plate from the rugose upper 

 border of the cavity. The front wall of the cavity slopes backward from the 

 upper angle to a little above the quadrate articular surface; its smooth wall 

 looks obliquely upward, backward, and outward. It seems probable that 

 this cavity, as thus bounded, was closed by a tympanic membrane, against 

 which the continuation of the stapes abutted. 



"The precise limits of the epiotic process are not certain, but a distinct 

 line Is evident on one side, indicating sutural attachment with the quadrate 

 along the posterior side of the platelike expansion and to within a short 

 distance of the articular projection. This, I am aware, is an unusual position 

 for the quadrate, with the earslit or opening above and In front of it, but there 

 can be no other Interpretation of the structure. The quadrate is well ossi- 

 fied below, fused with the extremity of the pterygoid on the Inner side and 

 with the quadratojugal in front below. 



"The occipital surface of the skull has, in the middle, a smooth, steep 

 declivity, with the small foramen magnum at the bottom, not more than 

 5 millimeters in diameter. The high rugosity of the posterior border of the 

 cranial table overhangs slightly this declivity, forming a fossa into which 

 doubtless were Inserted the strong neck muscles. Just outside of each con- 

 dyle there are the usual two cranial foramina at the base of the paroccipital 

 processes, which extend outward, joining the epiotic on the under side and 

 turning downward to terminate at or near the upper posterior corner of the 

 quadrate. Between this paroccipital process and the roof, at each side, 

 there is a moderately large post-temporal vacuity leading Into a deep cavity 

 just Inside the 'tympanic' rim of the ear cavity and below the roof of the 

 skull. 



"The structure of the under side of the skull, while not departing far 

 from the usual stegocephalan type. Is somewhat remarkable. The palatal 



* A closed otic notch is not unknown among Stegocephala. See Woodward, Proceedings of the Zoological 

 Society, 1904, p. 170, plate xi, Capilosaurus stantonensis Woodward. 



fThe plate references given in this description are for this paper, not the original. 



