SYSTEMATIC REVISION 



49 



Original description of Z. micro fthalmus: "Represented by an entire 

 skull covered with a thin layer of bean ore, and a second and larger skull 

 without lower jaw and with the extremity of the muzzle broken off. The 

 second specimen displays the characters of the base of the skull, and in 

 other respects better displays the specific characters. 



"The attenuation of the bones of the skull exhibited by the Z. serraius 

 is present in this species also. The interorbital and preinterorbital regions 

 are strongly concave, and there are strong preorbital fossae. The tabular 

 angles are very prominent, forming rudimentary horns, and there is a promi- 

 nent angle projecting from the posterior quadrate region. What especially 

 characterizes this species is the small size of the orbits. These are about 

 half the diameter of those of a Z. serratus of the same size, and are half the 

 diameter of the space between their posterior border and that of the cranium 

 at the middle line, and enter the interorbital width 2.5 times. The posterior 

 border of the orbit marks the fourth fifth of the length from the end of the 

 muzzle to the middle supraoccipital border. The muzzle narrows rapidly 

 anteriorly, presenting an elliptic outline, and is much depressed. 



A ^vy B 



Fig 8. — Zatrachys serratus. 



A. Left half of a skull with antorbital fossa freed from matrix. No. 4586 Am. Mus. X |. 



B. Upper view of skull. Antorbita! fossae are still filled with matrix. No. 4587 Am. Mus. X f . 



"The parasphenoid bone widens anteriorly so that the pterygoid foramina 

 are triangular with the base posterior and the apex anterior. At the extrem- 

 ities of the transverse processes of the parasphenoid the pterygoids send 

 a prominent border downwards; they then curve rather abruptly outwards 

 to the quadrates. The teeth have not been fully exposed, but on the middle 

 of the length of the maxillary bones they are small and widely spaced. 



"No. I. "Dimensions. mm 



Total length on middle line 100 



Width at orbits 84 



No. 2. 



Width at orbits 96 



Width between extremities of quadrates 13° 



Width between tabular horns 21 



Width between orbits 27 



Length from orbit to extremity of tabulare 4° 



4 



