258 -P^'<?/. 0. C. Marsh — New Jurassic Dinosaurs. 



as pubes ; while the pubes themselves have not been considered as 

 part of the pelvic arch. 



Fortunately, in the present specimen of Ceratosaurus, the ilium, 

 ischium, and pubes are firmly coossified, so that their identification 

 and relative positions cannot be called in question. The ilia, more- 

 over, were attached to the sacrum, which was in its natural place in 

 the skeleton, and the latter was found nearly in the position in which 

 the animal died. The pelves of Ceratosaurus and of Allosaurus are 

 shown in Figs. 5 and 6. 



The ilium in Ceratosaurus has the same general form as in Mega- 

 losaurus. In most of the other Theropoda, also, this bone has 

 essentially the same shape, and this type may be regarded as 

 characteristic of the order. In Creosaiirus, the anterior wing is more 

 elevated, and the emargination below it wider, but this may in part 

 be due to the imperfection of the border. 



The ischia in Ceratosaurus are comparatively slender. They 

 project well backward, and for the last half of their length the two 

 are in close apposition. The distal ends are coossified, and expanded. 



The pubes in Ceratosaurus have their distal ends coossified, as in 

 all the known Theropoda. They project downward and forward, 

 and their position in the pelvis is shown in Figs. 5 and 6. Seen 

 from the front, they form a Y-shaped figure, which varies in form in 

 different genera. The upper end joins the ilium by a lai'ge surface, 

 and the ischium by a smaller attachment. The united distal ends 

 are expanded into an elongate, massive foot, as shown in Figs. 5 

 and 6, which is one of the most peculiar and characteristic parts of 

 the skeleton. 



The pubes of Megalosaurus have not yet been identified, but there 

 can be little doubt that they are of the same general type as in 

 Ceratosaurus and Allosaurus. The pubes of Coelurus pertain to a new 

 species, which may be called Coelurus agilis. This animal was at 

 least three times the bulk of the type. Owen has figured the pubes 

 of another species of this genus, under the name PoiJcilopleuron 

 pusillus, but he regarded the specimen as an "abdominal haemapophysis 

 and ha?mal spine." (Palseontographical Society, vol. xxx. plate i. 

 1876.) 



The extremely narrow pelvis is one of the most marked features 

 in this entire group, being in striking contrast to the width in this 

 region in the herbivorous forms found with them. If the Theropoda 

 were viviparous, which some known facts seem to indicate, one 

 difficulty, naturally suggested in the case of a reptile, is removed. 



Another interesting point is, the use of the large foot at the lower 

 end of the pubes, which is the most massive part of the skeleton. 

 The only probable use is, that it served to support the body in sitting 

 down. That some Triassic Dinosaurs sat down on their ischia is 

 proved conclusively by the impressions in the Connecticut Eiver 

 sandstone. In such cases the leg was bent so as to bring the heel to 

 the ground. The same action in the present group would bring the 

 foot of the pubes to the ground, nearly or quite under the centre of 

 gravity of the animal. The legs and ischia would then naturally 



