] 06 Prof. 0. C. Marsh — A New American Jurassic Dinosaur. 



sauridce, the ischia are massive, and directed downward, with their 

 expanded extremities meeting on the median line. In the Morusauridm, 

 the ischia are slender, with the shaft twisted about 90°, directed back- 

 ward, and the sides meeting on the median line, thus approaching this 

 part in the more specialized Dinosaurs. The ischia referred to the 

 genus Biplodocus, representing the new family here established, are 

 intermediate in form and position between those above mentioned. 

 The shaft is not expanded distally, nor twisted, and was directed 

 downward and backward, with the ends meeting on the median line. 



a- 



Fig. 9. — Clievron found attached to 



tenth and eleventh vertebrsB of Fig. 10. — Chevron of another individual : 

 D. hngus, top and side views, top and side views ; size and letters as 



one-tenth natural size ; a, anterior in Fig. 9. 



end ; p, posterior end ; «;, faces 

 for articulation with vertehrse. 



Size and Halits. — The type specimen of Biplodocus, to which the 

 skull here figured apparently belongs, indicates an animal intermediate 

 in size between Atlantosaurus and Morosaurus, probably 40 or 50 feet 

 in length, when alive. The teeth show that it was herbivorous, and 

 the food was probably succulent vegetation. The position of the 

 external nares indicates an aquatic life. 



The remains of the above specimen were found by Messrs. S. "W". 

 "Williston and M. P. Felch in the Upper Jurassic beds, near Canon 

 City, Colorado. A second and smaller species is represented by 

 remains found by by Mr. Arthur Lakes near Morrison, Colorado. 

 This species, which may be called Biplodocus lactistris, has much more 

 slender jaws than the one above described. A maxillary bone contains 

 eight teeth, and at the premaxillary suture measures 26""*" in thick- 

 ness. The series of teeth occupy a space of 70""™. A second speci- 

 men of apparently the same species has since been found in Wyoming. 



The geological horizon of all the Sauropuda from the Rocky 

 Mountain region is in the Atlantosaurus beds of the Upper Jurassic. 

 !N^o Cretaceous forms of this group are known. 



Classificatioist. 



The main characters of the order Sauropoda, and of the three 

 families now known to belong to it, are as follows : 



Order Sauropoda. — Premaxillary bones with teeth. Large antorbital 

 opening. Anterior nares at apex of skull. Post-occipital bones. An- 

 terior vertebrse opisthocoelian ; pre-sacral vertebrae hollow; each sacral 

 vertebra supports its own transverse process. Fore and hind limbs 

 nearly equal ; limb bones solid. Feet plantigrade, ungulate ; five 



