176 REPORT—1874. 
External nasal foramina roundish, 
Mastodonsaurus, Capitosaurus, Dasyceps, Micropholis, Rhinosaurus, Bothriceps. 
Auditory opening indenting posterior margin of upper surface of skull. 
Mastodonsaurus, Eurosaurus, Trematosaurus, Dasyceps?, Micropholis?, Rhino- 
saurus, Loxomma, Archegosaurus. 
Auditory opening not indenting posterior margin of upper surface of skull. 
Pteroplax, Urocordylus, Keraterpeton. 
Epiotic cornua conspicuous. 
Dasyceps, Loxomma, Batrachiderpeton, Pteroplax, Urocordylus, Keraterpeton. 
Epiotie cornua inconspicuous or wanting. 
Mastodonsaurus, Capitosaurus, Trematosaurus, Micropholis, Rhinosaurus, Arche- 
gosaurus *. 
Mandible with well-developed postarticular process. 
Mastodonsaurus, Capitosaurus, Eurosaurus, Pachygonia ?, Trematosaurus, Gonio- 
glyptus, Diadetognathus, Anthracosaurus? 
Postarticular process of mandible inconspicuous or wanting. 
Micropholis, Loxomma, Archegosaurus. 
Mandible with internal articular buttress. 
Mastodonsaurus, Capitosaurus, Pachygonia ?, Gonioglyptus, Anthracosaurus, 
Mandible without internal articular buttress. 
Diadetognathus, Loxomma, Archegosaurus. 
Mandibular symphysis short, not exceeding twice the vertical depth of the 
ramus in front. 
Mastodonsaurus, Capitosaurus, Trematosaurus, Labyrinthodon, Archegosaurus, 
Keraterpeton. 
Mandibular symphysis long, exceeding twice the vertical depth of the ramus 
im front. 
Lepterpeton (upwards of one third the length of the skull). 
Maxillary teeth wanting. 
Batrachiderpeton, Pteroplax. 
Maxillary teeth equal or subequal. 
Mastodonsaurus, Capitosaurus, Trematosaurus, Gonioglyptus?, Dasyceps, Rhino- 
saurus, Zygosaurus, Pholiderpeton, Archegosaurus, Dendrerpeton. 
Mazillary teeth unequal. 
Labyrinthodon, Anthracosaurus, Loxomma. 
A transverse row of vomerine teeth. 
Mastodonsaurus, Metopias, Labyrinthodon. 
Vomerine teeth aggregated. 
Batrachiderpeton, Dendrerpeton +, Hylonomus +. 
Mandibular teeth (outer series where there are two) equal or subequal. 
Mastodonsaurus, Capitosaurus, Trematosaurus, Labyrinthodon, Diadetoenathus, 
Batrachiderpeton, Pholiderpeton, Archegosaurus, Dendrerpeton, Hylonomus, 
Hylerpeton. 
* In one example of A. Decheni the cornua are 4 in. long, the length of the skull along 
the middle line being 11 in. t Dawson. 
