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ON THE CLASSIFICATION OF THE LABYRINTHODONTS. ye 4 
Mandibular teeth unequal. 
Melosaurus, Anthracosaurus, Loxomma, Pteroplax. 
One or two mandibular tusks near the symphysis, forming a short inner series. 
Mastodonsaurus, Trematosaurus, Labyrinthodon. 
A numerous inner series of mandibular teeth. 
Dendrerpeton acadianum *. 
Teeth recurved at apex. 
Anthracosaurus, Rhinosaurus, Pholiderpeton, Dendrerpeton Oweni. 
Teeth with anterior and posterior cutting-edges. 
Loxomma. 
Dentine non-plicate. 
Dendrerpeton acadianum (outer premaxillary, maxillary, and mandibular series, and 
vomerine P teeth)+, Hylonomus, Hylerpeton. 
Dentine simply plicate, 
Archegosaurus. 
Dentine complex-plicate. 
Mastodonsaurus, Capitosaurus, Trematosaurus, Gonioglyptus, Labyrinthodon, Dia- 
detognathus, Anthracosaurus, Loxomma, Pteroplax. 
Lyra enclosing an oval or rounded space in front of the orbits. 
Mastodonsaurus, Trematosaurus, Metopias, Labyrinthodon, Brachyops. 
Lyra angulated. 
Gonioglyptus. 
i Lyra consisting of two straight or nearly straight lines, diverging in front. 
Loxomma, Zygosaurus. 
Lyra imperfect. 
Archegosaurus. 
Lyra absent. 
Rhinosaurus, Pteroplax ? 
Thoracic plates externally sculptured. 
Mastodonsaurus, Capitosaurus?{, Trematosaurus, Gonioglyptus?{, Archego- 
saurus, Urocordylus, Keraterpeton. 
Lateral thoracic plate with a reflected process. 
Mastodonsaurus, Capitosaurus, Trematosaurus. 
Vertebral column notochordal. 
Archegosaurus. 
Vertebral centra discoidal. 
Mastodonsaurus, Anthracosaurus, Loxomma, Ichthyerpeton, Pteroplax, Pholider- 
peton. 
* Dawson. 
+ The inner series on the premaxillz, maxillx, and mandible are described as plicated. 
The outer series (?) in the premaxille of D. Oweni are described by Dr. Dawson as plicated 
like the inner maxillary teeth. 
5 oa pectoral plates believed to belong to these genera are not certainly identified. 
. N 
