44 AMPHIBIA AND PISCES OF THE PERMIAN OF NORTH AMERICA 



equal tuberosities which are separated by a deep groove instead of one prom- 

 inent one. The external tuberosity is represented in the T. insignis by a 

 small protuberance of the lateral enlargement of the external face of the 

 ramus. The extremity of this tuberosity is in the T. bilobatus strongly 

 honeycombed, and it is bounded below and externally by a groove which 

 is faintly indicated in T. insignis. Above it, on the inner side, is another 

 shallow groove, from which it is separated by a sharp ridge. Both grooves 

 are smooth. The superior one is wanting in T. insignis. The quadrate 

 cotylus is more depressed externally than in T. insignis, thus making it more 

 oblique. The internal fossa of the cotylus is not divided by a longitudinal 

 groove, as it is in T. insignis. The dental foramen is large and is located as 

 in the T. insignis. There is also an inferior longitudinal groove of the ramus 

 as in that species. The surfaces preserved show that the sculpture is more 

 marked in the T. bilobatus than in the T. insignis. 



"Measurements, ^ 



"Depth of ramus at interior edge cotylus 0.026 



Length of ramus from interior edge cotylus 020 



Width of ramus at interior edge cotylus 017 



Width of both tuberosities of angle 0125 



Diameters of intercentrum: 



Anteroposterior on 



Transverse 021 



Thickness of intercentrum 004" 



Revised description: See table in revised description of T. insignis above. 



Trimerorhachis conangulus Cope. 

 Proc. Am. Phil. Soc, vol. xxxv, 1896, p. 137. 



Type: An imperfect skull. No. 4569 Am. Mus. Nat. Hist. Cope. Coll. 

 From Texas. 



Original description: " Size, the least of the species of the genus. Angle 

 of the mandible produced, conic. Orbits rather large, the posterior border 

 nearer the line of the end of the muzzle tnan to the posterior extremity of 

 the mandibular angle, but not so near as to the posterior border of the tab- 

 ular bone. External nares half-way between the orbit and the end of muzzle. 

 Interorbital width equal diameter of orbit. 



"Teeth small, the crowns elongate and acute. Twenty-two may be 

 counted from the posterior end of the series to a point opposite the anterior 

 border of the orbit. A much larger tooth is situated on the external border 

 of the maxillopalatine (vomer), a little distance in front of the choanse, while 

 an equally large one is situated directly on the posterior border of the latter. 

 Another tooth of equal size is situated external to the posterior tooth, near 

 the maxillary border, and the base of a smaller one is visible beneath the two. 



"The mandibular ramus becomes quite slender anteriorly. Posteriorly, 

 the sutures of the angular, articular, dentary, and splenial are distinct. The 

 symphysis projects beyond and turns up in front of the premaxillary border. 

 The angle projects considerably beyond the quadrate, and is rounded below 

 and at the sides. The extremity is vertically grooved, but whether acciden- 

 tally or normally I can not determine. 



"The elements comprising the cranial roof are mostly distinguishable. 

 The supraoccipitals have considerable extent on the superior face of the 

 skull. The largest bones are the parietals, whose median suture is inter- 



