\VlLLISTON.] 



Mosasaurs. 



217 



EXPLANATION OF PLATES. 



(Pages 223-347.) 



The following abbreviations apply to all the plates of the skull 



Ang, angular. 

 Art, articular. 

 Bo, basioccipital. 

 Bs, basisphenoid. 

 Cor, coronoid. 

 Dn, dentary. 

 Eo, exoccipital. 

 Fr, frontal. 

 Jug, jugal. 

 L, lachrymal. 



Max, maxilla. 

 Na, nares. 

 Oe, occipital condyle. 

 P, parietal. 

 Pal, palatine. 

 Pet, petrosal. 

 Pfr, prefrontal. 

 Pmx, premaxillary. 

 Po, postorbitofrontal. 

 Prs, prosquamosal. 



Prsp, preeplenial. 

 Ptg, pterygoid. 

 Q, quadrate. 

 aS\ squamosal. 

 So, supraoccipital. 

 Spl, splenial. 

 St, stapes. 

 Sur, surangular. 

 Tr, transverse. 

 V, vomer. 



PLATE X. — Skull of Clidastes velox Marsh, from the side. 



PLATE XI. — Skull of Clidastes velox Marsh, from above. 



PLATE XII.— Skull of Clidastes velox Marsh, from below. 



PLATE XIII. — Skull of Platecarpus coryphceus Cope, from the side. 



PLATE XIV. — Skull of Platecarpus coryphceus Cope, from above. 



PLATE XV. — Skull of Platecarpus coryphceus Cope, from below. 



PLATE XVI. — Skull of Tylosaurus proriger Cope, from the side. 



PLATE XVII. — Skull of Tylosaurus proriger Cope, from above. 



PLATE XVIII. — Skull of Tylosaw us proriger Cope, from below. 



PLATE XIX. — Skull of Mosasaurus horridus Williston, from the side. 



PLATE XX. — Skull of Mosasaurus horridus Williston, from above. 



PLATE XXI. — Skull of Mosasaurus horridus Williston, from below. 



PLATE XXII. — Upper figure, maxilla and mandible of Brachysaurus over- 

 tonii Williston (the articular and splenial bones are shown from the inner 

 side, the other bones from without ) ; lower figure, left mandible of Plate- 

 carpus coryphceus, from the inner side. 



PLATE XXIII. — Upper figure, left mandible of Clidastes westii Williston, 

 from the outer side ; lower figure, right mandible of Clidastes tortor Cope, 

 from the inner side. 



