SYSTEMATIC REVISION 



69 



^^Measurements. 

 "Diameter of centrum: m 



Longitudinal 0.0055 



Vertical 0038 



Transverse 0040 



Length of facet for neurapophysis 0035 



Width of neural canal 0020 " 



Revised description: Contained in the revised description of the family. 



INCERTAE SEDIS. 

 Suborder GYMNARTHRIA Case. 

 Bull. Am. Mus. Nat. Hist., vol. xxvai, 1901, p. 177. 

 Known from the skull only. 



1. Skull completely overroofed; no temporal foramina, but lower edge 



of temporal region cut away as in some of the turtles. Lyra {Car- 

 diocephalus) and parietal foramen {Gymnarthrus) present. 



2. Quadrate free, not covered by the prosquamosal. 



3. Quadratojugal absent and the prosquamosal reduced to small size or 



absent. 



4. Basisphenoid and parasphenoid forming a large plate on the lower 



surface of the skull. 



5. Lower jaw as long as the skull. 



Family GYMNARTHRIDyE Case. 



Characters given in the suborder. 



Gymnarthrus willoughbyi Case. 

 Case, Bull. Am. Mus. Nat. Hist., vol. xxviii. Art. xix, 1910, p. 177. 

 Broom, Bull. Am. Mus. Nat. Hist., vol. xxvui. Art. xx, 1910, p. 219. 



Type: A small skull. No. 4892 Am. Mus. Nat. Hist. From Wilbarger 

 County, Texas. 



Homoiype: A second skull. No. 4763 Am. Mus. Nat. Hist. Cope Coll. 

 Locality unknown. 



The teeth are blunt cones with no 

 indication of anterior and posterior cut- 

 ting edges. The three teeth anterior to 

 the last slightly larger than the others, 

 but all the teeth decreasing regularly in 

 size to the anterior end; this includes the 

 premaxillary teeth, so that there are no 

 enlarged incisors. Nine teeth in the max- 

 illary and three or four in the premaxil- 

 lary. A large parietal foramen. No lyra 

 present. 



This animal was originally regarded 

 as a reptile, but a comparison with the 

 type of Cardiocephalus sternbergi Broili 

 shows that the two forms are closely 

 related if not identical. Cardiocephalus 

 has distinct lyra and the parietal foramen is either absent or very small. For 

 these reasons Gymnarthrus is retained as a separate genus, but transferred 

 provisionally to the Amphibia. Broom (lO) regards it as probably amphibian. 



Fig. 16. — G.teilloughhyi. No. 4892. Am. Mus. X 4, 



A. Lateral view of skull. 



B. The same, a, lower surface; h, upper surface. 



