252 Prof. 0. C. Marsh — New Jurassic Dhwsaurs. 



Figs. 6«, 66. '■^ Turbo'" suleostoimis, Phillips. Kelloway Rock, Scarborougli; 



Leckenby Collection. Front and back view. 

 ,, 7. '^ Tufbo" siilciistoinus, Phillips. Kelloway Eock. ? Hackness. 



British Museum. 

 ,, 8. Amberlcya clavata, Bean, MS. Oxford Clay, Scarborough. British 



Museum. 

 „ 9«, b, c. Littorina biserta, Phillips. Dogger, Blue Wyke. Leckenby Col- 

 lection. Front, back, and portion enlarged. 

 ,, 10«, b, c. „ ,, var. unicarinata. Bean. Dogger, Blue Wyke. 



Leckenby Collection. Front, back, and portion enlarged. 

 ,, \\a,b,c. Amherlei/a biserta. Dogger, Blue Wyke. Jermyn Street Museum. 



Front, back, and portion enlarged. 

 „ 12, 12a. " Turbo melanioides.'" Bean, MS. Dogger, Blue Wyke. York 



Museum. Front view, and facsimile of aperture. 



11. — The Principal Chakacters of American Jurassic Dino- 

 saurs BELONGING TO THE OrDER ThEROPODA.^ 

 By Professor 0. C. Marsh, M.A., F.G.S. 

 Of Tale College, Newhaven, Ct., U.S.A. 



THE carnivorous Dinosauria form a well-marked order, which the 

 writer has called the Theropoda, in his classification of this 

 group.^ Although much has been written about these reptiles since 

 Buckland described ^legaloxaurus in 1824, but little has really been 

 made out in regard to the structure of the skull, and many portions 

 of the skeleton still remain to be determined. 



The fortunate discovery of two nearly perfect skeletons of this 

 order, as well as a number of others with various important parts of 

 the skeleton in good preservation, has afforded the writer an oppor- 

 tunity to investigate the group, and some of the results are here 

 presented. A more detailed description of these fossils, and others 

 allied to them, will be given in another communication. 



Of the carnivorous Dinosaurs from the American Jurassic, there 

 are four genera, which each represents, apparently, a distinct family. 

 These genera are AUosaurus, Coelurus, Labrosaurus, and the new 

 genus Ceratosaurus, here described. In the present article, AUosaurus 

 and Ceratosaurus will be mainly used to illustrate tlie more important 

 characters of the order, and the relations of the other genera to them 

 will be indicated in the classification presented in conclusion. 



The specimen of Ceratosaurus here first described presents several 

 characters not hitherto seen in the Dinosauria. One of these is a 

 large horn on the skull ; another is a new type of vertebra, as strange 

 as it is unexpected ; and a third is seen in the pelvis, which has the 

 bones all coossified, as in existing Birds. Archceopteryx alone among 

 adult birds has the pelvic bones separate, and this specimen of Cera- 

 iosaurus is the first Dinosaur found with all the pelvic bones anchy- 

 losed. Another feature of this skeleton, not before seen in the 

 Theropoda, is the presence of osseous dermal plates. These extend 

 from the base of the skull along the neck, over the vertebrse. The 

 plates appear to be ossified cartilage. 



1 From the American Journal of Science, vol. xxvii. April, 1884. 

 - Silliman's Journal, vol. xxiii. p. 81, January, 1882. See also vol. xxi. p. 423, 

 May, 1881 ; p. 339, April, 1881 ; and vol. xvii. p. 89, January, 1879. 



