l6o AMPHIBIA AND PISCES OF THE PERMIAN OF NORTH AMERICA 



Referred material: Numerous well-preserved teeth; fragments of spines; 

 several crania; the five teeth figured by Case, loc. cit., No. 6504 University 

 of Chicago. 



Original description: "Skull with massive walls. Form elongate, 

 depressed, the orbit not extending behind the anterior third of the length. 

 Basicranial and basifacial axes in one line, flattened, the supraorbital border 

 fiat, concave on the edge; postorbital processes obtuse, the temporal ridges 

 commencing with thin posterior border, which they excavate. The ridges 

 then turn, extend parallel posteriorly, terminating in the horn-like processes 

 already described, with a slight divergence. The apices mark the posterior 

 third of the length of the skull. The occipital condyle is wider than deep, 

 and its superior border retreats forwards so as to cause its cup to look 

 upwards. The exoccipital diameter at the foramen magnum is less than that 

 of the basicranial axis, the osseous element of which, probably sphenoid, is 

 recurved on the sides to their middle. The sides of the latter expand a 

 little to meet their lateral alae. Immediately above their contact is situ- 

 ated the supposed condyle for the hyomandibular element. The basicranial 

 axis is convex opposite the postorbital processes, from the bases of which 

 a concavity separates it. It has a slight median groove at this point. It is 

 much narrower than the interorbital width above. A short distance in front 

 of the postorbital processes it begins to contract, and gradually reaches an 

 acuminate apex. Superior to this apex, commencing posterior to it, the space 

 between it and the supraorbital or nasal elements is occupied by a massive 

 element (.'' ethmoid) which forms the floor of the nasal median fontanelle. 



"The surfaces are smooth, but readily weather so as to be granular. 

 The granules are subround, with flattened surface. 



"Measurements of skull. m 



"Total length of skull to end of frontal bone (No. i) 0.180 



Total length of muzzle to orbit; axial 024 



Total length of skull to postorbital process 058 



Total length of skull to apices of frontal cartilage 1 17 



Total length of skull to (?) pterotic apex (axial) 155 



Width of skull at prefrontals 045 



Width of skull at supraorbital borders 055 



Width of skull at ( ?) pterotic apices 088 



Width of occipital condyle 034 



Depth of occipital condyle 025 



" Measurements of jaws. m 



"Length of mandibular ramus from cotylus, inclusive 0.145 



Depth of mandibular ramus at cotylus 028 



Depth of mandibular ramus at middle _ _ 03S 



Length of palatopterygoid bone from cotylus, inclusive 14S 



Depth of palatopterygoid bone at postorbital articulation 071 



Depth of palatopterygoid bone at orbit _. 035 



Length of palatopterygoid bone posterior to orbit 070" 



Diacranodus platypternus (Cope). (Plate 30, fig. 8.) 

 1884. Didymodus platypternus Cope, Amer. Nat., xviii, p. 818, pi. xxiii, figs. 8. 9. 



1884. Didymodus platypternus Cope, Proc. Amer. Philos. Soc, xxi, p. ^§7, p'ate, 



figs. 8, 9. 



1885. Diacranodus platypternus (Cope), Carman, Bull. Mus. Compar. Zool., p. 30. 

 1890. Didymodus platypternus Cope, Trans. Amer. Philos. Soc, n. s., xvi, p. 285. 



Type: Numerous fragments of a pair of large jaws and two imperfect 

 teeth. No. 7243 Am. Mus. Texas. 



