ON THE CLASSIFICATION OF THE LABYRINTHODONTS. 175 
Macille deficient, premacille with free termination behind. 
Batrachiderpeton ?, Pteroplax ? 
Orbit round. 
Dasyceps, Rhinosaurus (irregular), Dendrerpeton. 
Orbit oval. 
Capitosaurus, Eurosaurus, Trematosaurus, Metopias, Brachyops, Micropholis, Both- 
riceps, Archegosaurus, Lepterpeton, Urocordylus, Keraterpeton. 
Orbit irregular-oval. 
Mastodonsaurus, Loxomma, Zygosaurus. 
Orbit large; not less than one fourth of the length of the skull. 
Brachyops, Micropholis, Loxomma, Keraterpeton*. 
Orbit moderate ; not less than one eighth of the length of the skull. 
Mastodonsaurus, Eurosaurus, Rhinosaurus (nearly +), Bothriceps (nearly }), Zy= 
gosaurus (nearly +), Archegosaurus latirostris, Lepterpeton. 
Orbit small; less than one erghth of the length of the skull. 
Capitosaurus, Trematosaurus, Metopias, Dasyceps, Archegosaurus Decheni. 
Orbit central. 
Trematosaurus, Micropholis, Rhinosaurus, Bothriceps, Loxomma (slightly posterior), 
Zygosaurus (slightly posterior), Lepterpeton. 
Orbit anterior. 
Metopias, Brachyops, Batrachiderpeton, Keraterpeton. 
Orbit posterior. 
Mastodonsaurus, Capitosaurus, Hurosaurus, Dasyceps, Archegosaurus. 
Interorbital space equal to transverse diameter of orbit. 
Eurosaurus, Rhinosaurus, Loxomma, Keraterpeton. 
Interorbital space greater than transverse diameter of orbit. 
Capitosaurus, Trematosaurus, Metopias, Dasyceps, Brachyops, Bothriceps, Zygo- 
saurus, Archegosaurus, Dendrerpeton. 
Interorbital space less than transverse diameter of orbit. 
Mastodonsaurus, Micropholis. 
Palatine foramina large, approximate. 
Mastodonsaurus, Capitosaurus, Trematosaurus, Gonioglyptus, Metopias, Archego- 
saurusf. 
Palatine foramina small, distant. 
Dasyceps, Anthracosaurus, Loxomma ? 
External nasal foramina relatively near. 
Mastodonsaurus, Trematosaurus. 
External nasal foramina relatively distant. 
Capitosaurus, Metopias, Dasyceps, Micropholis, Bothriceps, Loxomma, Archego- 
saurus, Dendrerpeton, 
External nasal foramina oval. 
Trematosaurus, Metopias, Loxomma, Archegosaurust, Dendrerpeton§. 
* Not including the epiotie cornua in the length of the skull. 
+ Inferred from the slenderness of the processus cultriformis of the parasphenoid. 
t Or hippocrepiform. § Trausyersely oval; longitudinally oval in the rest. 
