156 DINOSAURS OF NORTH AMERICA. 



gate, and were locked together by strong zygapophyses. The first 

 three or four behind the axis had the front articular face of the cen- 

 trum somewhat convex, and the posterior one deeply concave. All 

 the other cervicals were biconcave, as were also the vertebrae of the 

 trunk and tail. The articular faces of the cervicals are inclined, show- 

 ing that the neck was curved. The anterior cervical ribs were coossified 

 with the centra, as in birds. Figs. 2, 2a, and 2b, PI. VII, represent a 

 cervical vertebra from near the middle of the neck. The cavities in 

 the cervicals are connected with the outside by comparatively large 

 pneumatic openings. The neural canal is very large, and traces of the 

 neurocentral suture are distinct. 



The dorsal vertebrae of Coelurus are much shorter than the cer- 

 vicals. The centra have a deep cup in front and a shallow concavity 

 behind. These articular faces are nearly at right angles to the axis of ' 

 the trunk. The neural spine is elevated and compressed. The trans- 

 verse processes are elongate. The ribs preserved have undivided 

 heads. A posterior dorsal is represented in PI. VII, figs. 3, 3a, and 36. 

 The suture of the neural arch is distinct in this specimen. The foramina 

 leading to the cavities in the dorsal vertebras are quite small. 



The caudal vertebra; are elongate and very numerous. They are all 

 biconcave, and all appear to have been without chevron bones. An 

 anterior caudal is figured in PI. VII, fig. -4, and the accompanying 

 section shows the inner structure. In most of the caudals, the neuro- 

 central suture has entirely disappeared. 



THE MIND l.IMBS. 



The limb bones of Coelurus are very hollow, and some of them appear 

 pneumatic. The metatarsals are quite long and slender. The terminal 

 phalanges of the hind feet are pointed, and in life were evidently covered 

 with sharp claws. The ilium is of the Megalosaurus type. The pubes 

 are slender, strongly coossified with each other, and terminated below 

 by a large foot-like process, as shown in PI. X, figs. 3 and 4. 



The characters of Coelurus are so distinctive that it appears to 

 represent a separate family, which has been called by the writer the 

 Coelurida;. Several species of the genus are known in this country, all 

 of moderate dimensions, varying in size from that of a fox to that of a 

 wolf. Nearly all are from the Atlantosaurus beds of the West, but one 

 small species has been found in the Potomac beds on the Atlantic Coast. 



CERATOSAURUS. 



The most interesting carnivorous dinosaur from the American Juras- 

 sic, and the one best known, is Ceratosaurus, which differs so widely 

 from the typical forms that it has been regarded as representing a dis- 

 tinct suborder. The type specimen of Ceratosaurus, described by the 

 writer in 1884, presented several characters not before seen in the 

 Dinosauria. One of these is a horn core on the skull ; another is a 



