34 AMPHIBIA AND PISCES OF THE PERMIAN OF NORTH AMERICA 



to the apex, or farther. One large and one medium-sized teeth stand on 

 each dentary bone near the symphysis, and there are two similar ones at a 

 point further back on the same bone. Near the anterior part of the maxillary 

 below the ( }) nostrils, is a huge tooth, with a graduated series of small teeth 

 posterior to it, and a very small one anterior to it. 



"The neural arch of a vertebra has a well-developed vertical spine. Its 

 neurapophysis rested in an oval fossa of the centrum which probably was 

 divided into pleurocentra. The prezygapophyses are very small and look 

 directly upwards. The postzygapophyses are much larger and look obliquely 

 outwards and backwards. The spine is not expanded at the summit and is 

 granular, as though it was protected by a cartilaginous cap. Its section 

 is anteroposteriorly lenticular, with acute edge (angle) posteriorly and a 

 very narrow truncate edge anteriorly. The latter is bounded below just 

 above the root of the neural arch by two little fossae. The posterior keel 

 is bounded below by a corresponding single fossa. The posterior acute 

 edge of the spine is dentate and the surface on each side of it is beveled 

 with rabbeted surfaces as though for a coarse squamosal suture. But the 

 appearance of suture is fallacious, and is simply due to contraction of the 

 transverse diameter of the spine. The neurapophysis is much narrower 

 antero-posteriorly than the neural spine. 



"Measurements. 



M 



"Depth of maxillary bone at large anterior tooth 0.037 



Depth of dentary at symphysis 025 



Depth of dentary near middle 021 



Width of dentary near middle 015 



Diameter of base of large maxillary tooth oio 



Diameter of small maxillary tooth 0035 



Length of small maxillary tooth 008 



Length of large mandibular tooth near symphysis 016 



Diameter of base of crown of do 006 



Elevation of neural arch 037 



Diameters neural spine, vertical 029 



Diameters neural spine, at apex: 



Anteroposterior 019 



Transverse 012 



Width neurapophysis anteroposteriorly 010" 



Revised description of the genus and species: This genus and species are 

 known only from a few fragments of the jaws and other bones and can not 

 be compared with the other members of the family Eryopidce^ in which it 

 is provisionally placed. The sharp, rather recurved teeth and the peculiarly 

 imbricate appearance of the surface of the bone are totally different from 

 any other form from the Texas beds. 



Genus ACHELOMA Cope, 

 Proc. Am. Phil. Soc, vol. xx, 1882, p. 455; Am. Nat., vol. xviii, 1884, p. 35. 



Type: A skull with a good portion of the vertebral column and some 

 of the limb bones. No. 4205 Am. Mus. Nat. Hist. Cope Coll. From Texas. 



Original description: "Order Rhachitomi; family Eryopidse, differing from 

 Eryops in the absence of notch of the posterior border of the skull between 

 the epiotic and quadrate or squamosal bones, and in the absence of condyles 

 of the humerus. 



