66 AMPHIBIA AND PISCES OF THE PERMIAN OF NORTH AMERICA 



Aspidosaurus crucifer Case. 

 Zatrachys crucifer, Case, Journ. Geol., vol. xi, 1903, p. 399. 



Type: A single neural spine. No. 171 University of Chicago. From 

 Texas. 



Original description: As shown in the accompanying figure, "the spine 

 has a cruciform shape with a sharp upper portion and short lateral processes. 

 The posterior zygapophyses are preserved and are relatively small. The 

 upper faces of the lateral processes and the apex of the spine are pitted by 

 a deeply marked rugosity so that the whole upper surface of the spine is 

 excavated by deep pits of a size and depth seen before only in the larger 

 amphibians, Eryops and Cricotus. The lower surfaces of the lateral pro- 

 cesses and the sides of the base of the spine are smooth. The anterior and 

 posterior edges of the apex are free from the deep pits and are marked by a 

 narrow space of striations showing that the spine was overlapped by the 

 edges of some other element; it is evident from the shape of the spine that 

 this could not have been the edges of the adjacent spine, but must have 

 been an extra element intercalated between the spines, probably one of 

 the dermal ossifications such as occur along the spines of Pareiasaurus. The 

 nearest approach to this condition is found in the rugose expanded apices 

 (of the spines) of Zatrachys apicalis Cope, and so I have referred this speci- 

 men to that genus, until further information may be obtained. The frag- 

 ment is .054 m. in height and .058 m. across the lateral processes." 



Revised description: 



I. Only a single neural spine known. The apex with a prominent 

 median spine and narrow lateral process. Adjacent process 

 touching, but overlapping very slightly. 



Family TREMATOPSID^ Williston. 

 Bull. Geol. Soc. Am., vol. 21, 1910, p. 278. 



Original description: "A median foramen back of premaxillae; large 

 antorbital vacuities. Otic notch wholly inclosed by bone, the opening small 

 and extending far forward. Palate with two pairs of large teeth back of 

 the nares and a single one on each vomer. No parasphenoid. Ribs short, 

 the anterior ones expanded distally. Twenty-two or twenty-three pre- 

 sacral vertebrae; a single sacral; tail short. No dermal armor or carapace. 

 Cleithrum unknown. Clavicles and interclavicle small, without dermal 

 pittings. Humerus with ectepicondylar process." 



Revised description: 



1. Small, about 500 cm. long, head disproportionately large. 



2. Occipital condyles separate. 



3. Otic notch small, completely closed, forming a fenestra. 



4. Parasphenoid vestigial, or absent. 



5. One functional sacral rib. 



6. No armor on back. 



7. Clavicles and interclavicles without external sculpture. 



8. Cleithrum unknown, probably present. 



9. Humerus with ectepicondylar process as in Eryops. 



ID. Femur with prominent ridge on posterior face resembling Eryops. 



11. The two halves of the neural spine united. 



12. Intercentra thick, constricting the notochordal space. No pro- 



cesses on the sides of the intercentra for the ribs. 



