AMERICAN LABYRINTHODONTIDM 583 



but takes no part in the symphysis. It occupies the upper half of 

 the inside of the mandible, and is very thin. 



Below the splenial, and in front of the angular, an element that 

 seems to be separate from the dentary is present. The suture between 

 it and the dentary is not distinct, but at the symphysis the dentary 

 seems to be separate from it. This seems to be a separate element 

 in Eryops also, but the evidence is not conclusive in either case. 



On the upper border of the mandible, just in front of the cotylus, 

 there is an opening for Meckel's cartilage. For convenience in 

 description, this is called the supra-meckelian foramen. Perhaps 

 a name has been given to it previously, but, if so, the writer has failed 

 to find it. It is subtriangular in shape, 85 mm long by about 4o mm 

 in greatest width. On the inner side the articular projects farther 

 forward than on the outer, making the posterior margin of the foramen 

 diagonal to the long axis of the jaw. The apex of the foramen lies 

 between the splenial and coronoid, while the inner and outer sides 

 are formed by the prearticular and surangular. 



The jaw is hollow throughout, the bones forming a mere shell, 

 usually only a few millimeters in thickness. The cavity extends 

 from the symphysis to the tip of the postcotyloid process with its 

 greatest size in the region of the prearticular foramen. 



The vertebra,. — As before stated, there are about forty vertebrae 

 referred to Anaschisma in the collection, but none of them has the 

 arch preserved. Among them are two imperfect atlases of an oval 

 shape, about 7o mm broad by 5o mm high. Anteriorly they have two 

 slightly concave faces for articulation with the condyles; posteriorly 

 they are concave. A supposed axis is oval, and about the same size 

 as the atlas. It is opisthocoelous. On each side at about the middle 

 of the vertebrae there is a large, shallow facette for the articulation 

 of a rib. The thoracic vertebrae are nearly circular in shape, varying 

 from 40 to 65 mm in diameter. One of these shows that the ribs were 

 borne on exogenous processes arising from both the arch and body. 

 The caudals are smaller, proportionally longer, with" the vertical 

 diameter greater than the transverse. All of the vertebral articular 

 surfaces are for the articulation of single-headed ribs. 



Among the vertebrae present there are three others besides the 

 axis that are opisthocoelous. Whether they belong to a different 



