SYSTEMATIC REVISION 67 



Genus TREMATOPS Williston. 

 Trematops milleri Williston. 

 Journ. Geol., vol. xvii, 1909, pp. 636-658. 



Type: A nearly complete skeleton, No. 640 University of Chicago. 

 From Wilbarger County, Texas. 



Original description of the genus and species (abstracted from Williston's 

 description) : Skull triangular, the width posteriorly, but slightly less than 

 the length of the middle line. Surface deeply and coarsely pitted but with 

 no trace of lyra. Facial region markedly constricted just anterior to the 

 orbits; posterior to the orbits the skull is broad and flat. A median, un- 

 paired opening on the anterior portion of the snout opening into a palatine 

 vacuity. Two large antorbital openings, perhaps the nares, with septomaxil- 

 lary bones. Temporal fenestrse present. Parietal foramen small. Sutures 

 mostly indistinguishable, such as are made out shown in fig. 3, plate 14. 

 Occipital condyles paired; parasphenoid absent (?). A large tooth just 

 anterior to the internal nares, probably on the vomers. Four large teeth 

 on each palatine, arranged in pairs. Twenty-five or twenty-six teeth in 

 each maxillary and mandible. Twenty-three to twenty-five presacral ver- 

 tebrae. Two sacrals. Vertebrae rhachitomus. Ribs expanded at the extrem- 

 ities, little curved. Scapulacoracoid similar to that of Eryops; cleithrum 

 absent (.''); clavicle and interclavicle small, without sculpture on the outer 

 surfaces. Humerus similar to that of Eryops. Pelvis resembling that of 

 Eryops in general. "The femur resembles in miniature that of Eryops." 

 Twelve tarsal bones, three in the proximal row, four in the middle and 

 five in the distal row. The digits short and heavy with clawless, terminal 

 phalanges. Phalangeal formula, as preserved, i, 2, 3,4, 2; possible formula 

 due to the addition of a small ossicle to the first, second, and fifth digits, 



2, 3, 3, 4. 3- 



Revised description of the genus and species: 



1. Skull triangular, abruptly narrower anterior to orbits. 



2. Orbits in middle of skull looking upward. 



3. Nares united with elongate antorbital openings. 



4. A single, medial opening at extremity of nose. 



5. Otic notches in the form of fenestrae. 



6. Maxillary and mandibular teeth subequal, conical. A single 



tusk on the prevomer and two pairs of tusks posteriorly, 

 probably on the palatine and maxillary. 



7. Humerus with an ectepicondylar process and short entepicondy- 



lar process. Condyles well developed. 



8. Femur with a thin ridge on the posterior face. 



9. Twelve tarsal bones. 



10. Phalangeal formula of hind foot 2, 3, 3, 4, 3- Terminal pha- 

 langes without claws. 



