48 AMPHIBIA AND PISCES OF THE PERMIAN OF NORTH AMERICA 



a single series, and their bases are anchylosed to the bottom of a shallow 

 groove. The external boundary of this groove is more prominent than the 

 internal, so that the attachment of the teeth is shortly pleurodont. The 

 teeth have conic crowns, and have basal grooves indicating the dentinal 

 inflexions common to this group. The maxillary and other bones are charac- 

 terized by their strong sculpture, in the former the ridges being developed 

 into prominent tubercles in various places." 



In the "American Naturalist" Cope added: 



"The genus was originally represented by a maxillary bone, which sup- 

 ports teeth of unequal length, and whose surface is extraordinarily rugose. 

 In the typical species, Z. serratus, the rugosities project in the form of teeth 

 along the external alveolar border. Individuals with sculptured neural 

 spines and dermal bones are referred here. The intercentra are much like 

 those of Eryops and Acheloma." 



Revised description (skull only known) : 



1. Small, not exceeding 500 centimeters in length. 



2. Skull less elongate; elevated in orbital region. Orbits in pos- 



terior third of the skull; rims elevated, a strong interorbital 

 depression. 



3. Nares far back. 



4. Deep preorbital depressions. 



5. Sculpture not certain, surface destroyed in specimens preserved. 



Bones show a strong radial structure. Sutures very compli- 

 cated, long processes from edges of bones, interlocking 

 strongly. 



6. Tabulare prolonged into points. Posterior edge of skull more 



deeply concave. 



7. Occipital condyle divided. 



Zatrachys serratus Cope. 

 Z. serratus, Proc. Am. Phil. Soc, vol. xvii, 1878, p. 523. 

 Z. viicropthalmus Cope, Proc. Am. Phil. Soc, vol. xxxiv, 1896, p. 452. 



Neotype of Z. serratus the same as the genus. 



Type of Z. micropthalmus, a skull No. 4586; paratype, a skull No. 4587 

 Am. Mus. Nat. Hist. Cope Coll. 



Original description ofZ. serratus: "The horizontal expansion of the maxil- 

 lary bone is a character of this species, so that its plane forms an obtuse 

 angle with that of the long axes of the teeth. It presents no palatal lamina. 

 The teeth are separated by intervals of greater width than the diameter 

 of the base. The border of the bone above the teeth is thickened, and the 

 ridges are developed into numerous tubercles. These project externally 

 so as to form a prominent serrate margin entirely overhanging the external 

 alveolar border. The ridges diverge inwards in a radiating manner. The 

 surface is otherwise irregular from the presence of a deep fossa on the outer 

 side within the inner alveolar border. 



"Measurements. ^ 



"Length of fragment 0.018 



Width of fragment 018 



Width of fragment, alveolar groove 002 



Length of prominences beyond alveolar border 003 



Diameter of a tooth basis 001 



Three teeth in 005" 



