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PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXXVI. 



border it sends back a thin, finger-like process which laps along the 

 anterior internal surfaces of the angular and prearticular. From 

 an examination of mutilated specimens it appears there was a long 

 tapering anterior process which covered over the mandibular fossa 

 in the dentary, and extended nearly to the anterior symphysisal end. 

 It met the coronoid by a horizontal suture below the level of the 

 functional teeth (see fig. 2, Plate 9). The median ventral border 

 is swollen transversely and extends below the dentary and angular, 



and is visible from a lateral 

 ' view of the mandible. 



a be Coronoid. — The coronoid 



is a small, flattened bone 

 roughly triangular in outline. 

 It unites vent rally with the 

 splenial, dentary, and sur- 

 angular, and the lower ex- 

 ternal surface laps along the 

 internal surface of the short 

 dorsal process of the dentary, 

 extending above it and ter- 

 minating in a compressed, 

 rounded end. Its general 

 outline is shown at co., fig. 2, 

 Plate 9. 



Predentary. — The preden- 

 tary is unknown, but after a 

 comparison of camptosaurian 

 remains with those of allied 

 forms, I am inclined to the 

 opinion that when found it 

 will be more after the pat- 

 tern of Iguanodon than of 

 Triceratops^ as Marsh has in- 

 dicated it in the first restora- 

 tion of the mandible. In the 

 restoration of the skull (see 

 fig. 2) , the predentary as drawn is a modification of that of Iguanodon. 

 The teeth. — The teeth of both upper and lower jaws when unworn 

 are spatulate with serrated margins. A representative tooth selected 

 for description from the maxilla measures 38 mm. in length, of which 

 19 mm. belong to the crown. The root is cylindrical, gradually taper- 

 ing from the base of the crown to its end. As shown by broken teeth, 

 there was a large pulp cavity extending well up into the crown. The 

 outer surface of the upper and the inner surface of the lower teeth are 

 sculptured by longitudinal ridges passing from the union of the 



Fig. 9. — (1) Tenth upper tooth; (2) fifth 

 LOWEK tooth of Camptosaurus medius 

 Marsh. No. 1880, Yale Museum. Holo- 

 type. Nat. size, a, outer view ; h, view 



OF POSTERIOR BORDER ; C, INNER VIEW. AfTEE 



Marsh. 



