Marsh — Restorations of Claosaurus and Ceratosaurus. 349 



The pubes have their distal ends co-ossified, and expand into 

 an elongate, massive foot, which is one of the most character- 

 istic parts of the skeleton. It is probable that this foot in 

 connection with the distal ends of the ischia 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 River sandstone. In such cases, the leg 

 was bent so as to bring the heel to the ground. The same 

 action in the present reptile would bring the foot of the pubes 

 to the ground, nearly or quite under the center of gravity of 

 the animal. The legs and ischia would then naturally aid in 

 keeping the body balanced. Possibly this position was assumed 

 habitually by these ferocious biped reptiles, in lying in wait 

 for their prey. 



The femur is much curved, and the shaft very hollow. The 

 tibia is shorter than the femur, nearly straight, and has a large 

 cnemial crest. The astragalus is not coossified with the tibia, 

 and has a strong ascending process. The fibula is well devel- 

 oped, and nearly straight, its distal end fitting into the cal- 

 caneum. The tarsals of the second row are very thin, and 

 united to the metatarsals below them. 



The most interesting feature in the extremities of this 

 Dinosaur is in the metatarsal bones, which are completely 

 ankylosed, as are the bones of the pelvis. There are only 

 three metatarsal elements in each foot, the first and fifth 

 having apparently disappeared entirely. The three metatar- 

 sals remaining, which are the second, third, and fourth, are 

 proportionally shorter and more robust than in the other 

 known members of the T/ieropoda, and being firmly united 

 to each other, they furnish the basis' for a very strong hind 

 foot. The phalanges of the hind feet are of moderate length, 

 and most of them are quite hollow. The terminal phalanges 

 evidently supported strong and sharp claws. 



The unique cervical vertebrae, the coossification of the pelvic 

 bones, and the union of the metatarsals, as in modern Birds, 

 distinguish Ceratosaurus widely from all other Dinosaurs, and 

 make it the type of a well-marked family, the Ceratosauridw. 

 The nearest allied form is_apparently Omithomim.us, from the 

 Laramie, recently described by the writer. 



The type specimen of Ceratosaurus was about twenty-two 

 feet long when alive, and twelve feet high as here restored. 

 It was found by Mr. M. P. Felch, in the Atlantosaurus beds 

 of the upper Jurassic in Colorado. The associated fossils were 

 mainly other Dinosaurs, especially Sauropoda and Omithojpoda, 

 together with various small mammals. 



New Haven, Conn., September 22, 1892. 



