566 Reviews — Geological Survey of England and Wales. 



Mandible. 



Maxilla. 



Premaxilla. 



w 

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An extremely thin plate. 

 Symphysial surface very 



narrow, with ridge and 



groove. 

 No external bony layer. 



Two rows of dot-like 

 beak teeth. 



No median tooth. 



Numerous dot-like teeth, 

 confined to the ex- 

 treme oral margin. 



Maxilla not known. 



Premaxilla not known. 





Thin and plate-like. 

 Symphysial surface very 



narrow, with ridge and 



groove. 

 No external bony layer. 



Two or more beak teeth. 



One mediah tooth. 



Outer teeth usually nu- 

 meroxis and dot-like. 



Inner teeth variable; a 

 sen'es of small teeth 

 upon the outer margin. 



No bony layer upon ex- 

 terior. 



Much like Ischyodus in 

 form. 



Oral margin has teeth. 





 o 



a 



o 



CO 



More or less massive. 

 Symphysial surface narrow, 



with groove and ridge 



above. 

 Well-defined bony layer 



upon exterior near oral 



margin. 

 Usually one beak tooth, 



sometimes several. 



One median tooth. 



Usually two outer teeth, 

 sometimes several small 

 ones. 



Four teeth, two inner, one 

 outer and one median. 



Bony layer upon exterior 

 near oral margin. 



More or less quadrate in 

 side view, more robust 

 than in Edaphodon. 



Post oral region not laterally 

 expanded and usually has 

 a definite bony thickening 



Oral margin has teeth. 



^25 

 O 

 

 O 



w 

 o 



Massive. 



Symphysial surface wide, no 

 definite ridge or groove. 



Usixally no definite bony 

 layer upon the exterior 



One beak tooth and occa- 

 sionally a smaller one 

 above it. 



One large median tooth, 

 sometimes divided longi- 

 tudinally. 



Usxxally two oxxter teeth. 



Three teeth, two inner and 

 one outer. 



Apparently no external 

 bony layer. 



More or less triangular in 

 side view ; flatter than in 

 Ischyodus. 



Post oral surface laterally 

 expanded ; no bony thick- 

 ening. 



Oral margin has teeth. 



IB 



p 

 W 

 o 



IZi 



o 



Hi 



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 <J 



Massive. 



Symphysial surface nar- 

 row. 



Distinct bony layer xxpon 

 exterior near oral mar- 

 gin. 



No beak tooth. 



One large median tooth. 



No outer teeth ; oral 

 margin sharp. 



One large median tooth 

 divided into two pro- 

 cesses anteriorly. 



Bony layer xxpon exterior 

 near oral margin. 



Elongated from before 

 backwards. 



Oral sxxrface triangular 

 with prominent ridge 

 near symphysis. 



No teeth. 



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