ene SPT RE Ce Lee Ree SE ee ae sn, ESAT ey ec eaten ee Eee ee Ree eS ST 
O. C. Marsh—American Jurassic Dinosaurs. 91 
The large bones in Al/osaurus are hollow, and the metatar- 
'sals slender. The termina phalanges were armed with sharp 
claws. With the remains described above, a large spine was 
found, similar in general form to that of Omosaurus armatus 
described by Owen. 
The type of Adlosaurus is A. fragilis,* the remains of which 
indicate a reptile probably twenty-five feet in length, and of 
slender proportions. 
e genus Creosaurus appears to be most nearly related in 
its vertebre and ilium to Megalosaurus. It has apparently one 
less vertebra in its sacrum, and the ilium has in front of its pu- 
bic process an articular face which has not been observed in 
the latter genus. The position of this surface is indicated in 
Plate X, figure 1, 4, and it may have supported a prepubic 
bone. The sacral vertebra are elongated, and the transverse 
processes are placed higher up on the centra than those in Ad/o- 
saurus. The teeth in both genera are of the Megalosaurus type, 
and in the whole group are so similar as to be of little value 
for the determination of species. The type of Creosaurus, is 
C. atrox,t a reptile about twenty feet in length. 
A third genus of carnivorous Dinosaurs contains individuals 
of somewhat smaller size, and of this group the species named 
Allosaurus lucarist is the type. The cervical vertebre are short 
and strongly opisthoccelian, and the dorsals moderately so. 
ll these vertebrae have very large cavities in the centra, which 
connect with the exterior by a comparatively small foramen on 
each side. The neural spines of the dorsal vertebre are elevated 
and transverse, and the vertebrae now known do not show the 
diplosphenal articulation. The fore limbs in this genus are 
quite small, and the humerus is curved, and has a large radia 
crest. This genus is distinct fron Allosaurus, and may be called 
Labrosaurus, the type being Labrosaurus lucaris. 
ll of the carnivorous Dinosaurs known from the Atlanto- 
saurus beds appear to have moved mainly on the posterior limbs. 
The large bones were hollow, and many of the vertebre, as wel 
as some of the feet bones, contained cavities, or were otherwise 
lightened to facilitate rapid movement. 
specimens, from the same localities and horizon, some of which 
pertain to the same skeletons as those here illustrated. e 
_ careful investigation of this entire series will require much time, 
_ but promises important results. 
* This Journal, vol. xiv, p.515. + Ibid., vol. xv, p. 243. 
} Ibid., vol. xv, p. 242. 
