42 Hevieics — U. S. Geological Survey — 



alligator, if the weight of the entire animal be brought into com- 

 parison ; indeed, it may be said to have had one of the smallest brains 

 of any known land vertebrate. The teeth are small, with compi-essed, 

 fluted crowns, separated from the roots by a more or less distinct 

 neck. Owen's genus Omosaiirus, from the Kimmeridge Clay of 

 England, cannot be separated generically from Stegosaurns. Scelido- 

 suurus, from the Lias of Charmouth, also agrees with it in the 

 structure of its teeth and in the possession of dermal armour. 



In Camptosaurtis we have a form of dinosaur which in general 

 appearance resembles the Iguanodon from Bernissart. The sternum 

 in Camptosaurtis, however, is entirely unossified, and no trace of 

 clavicles has been found. In the manus of Camptosaunis there are 

 five functional digits, the first being flexible and parallel to the 

 second, not stiff and divergent like the thumb of Iguanodon. The 

 pes (hind-foot) has three functional digits only, the first being 

 rudimentary and the fifth entirely wanting (as shown on plate Ivi). 

 It is a more slender form than Iguanodon. Bryosaurus is a genus 

 allied to Camptosaurus, also from the Atlantosaurus beds of Colorado 

 and Wyoming. 



Laosauius is a diminutive dinosaur possessing many avian features, 

 now only seen in existing, and more especially in struthious, birds. 

 The European representative of Laosauvus is the HypsilopJiodon 

 Foxii of the Wealden of the Isle of Wight. Nanosaurus agilis is 

 the name given to another, quite small dinosaur, allied to the fore- 

 going, having strong bird-like characters in its anatomy. 



The Ceratopsidje, or huge horned dinosaurs from the Cretaceous 

 rocks, are an outcome of Converse County, Wyoming, where, in 

 a limited area near the Cheyenne River, Mr. J. B. Hatcher found 

 more than thirty specimens. In the largest individuals the skull 

 (in Triceratops) exceeds that of any land animal hitherto discovered, 

 living or extinct, and is only surpassed by some of the marine 

 Cetacea. One head, when complete, must have been 7 or 8 feet 

 long. Two others, nearly perfect, from the same horizon, have 

 equal or still greater dimensions.' Another striking feature is 

 its armature. This consisted of a sharp cutting beak in front, 

 a strong horn on the nose, a pair of very large pointed 

 horns on the top of the head, and a row of sharp projections 

 around the margin of the posterior crest. All these had 

 a horny covering of great strength and power. For offence and 

 defence they formed an armour ibr the head as complete as any 

 known. In some forms the armature extended over portions of 

 the body. The skull is wedge-shaped in form, the facial portion 

 being very narrow in front, and prolonged ; the frontal region is 

 massive and greatly strengthened to support the large and lofty 

 horn-cores which formed the central features of the armature. The 

 huge, expanded, posterior crest, which covered the back of the skull 

 and overshadowed the neck, afforded attachment to the powerful 

 ligaments and muscles that supported the head. Several other 

 genera, as Torosaurus, Ceratops, Sterrliolophus, Agathaumas, Polyonax, 

 and Mouoclonius, are referred to, and the first two are figured. One 



