THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE ill. VOL. VIII. 



No. VI.— JUNE, 1891. 



o:Eixo-xisrj^iLi ^^leTXOLiES. 



I. — The Gigantio Ceratopsid^, or Horned Dinosaurs, of 



North America.^ 



(PAET II., continued from p. 199.) 

 By Prof. 0. C. Marsh, Ph.D., LL.D., F.G.S., etc. 



The Scapular Arch and Fore Limbs. — The scapula is massive, 

 especially below. The shaft is long and narrow, with a thin edge 

 in front, and a thick posterior margin above the glenoid fossa. The 

 distal portion has a median external ridge, and a thick end (Wood- 

 cut, p. 242, Fig. l,sc.). 



The coracoid is rather small, and in old individuals may become 

 united to the scapula. It is sub-rhombic in outline, and is perforated 

 by a large and well-defined foramen. No indications of a sternum 

 have yet been found in this group (Woodcut, Fig. 1, cr.). 



The humerus (Fig. 2) is large and robust, and similar in form 

 to that of Stegosaurus. It is nearly as long as the femur in one 

 individual, proving that the animal walked on all four feet. The 

 radius and ulna (Fig. 3) are comparatively short and stout, and the 

 latter has a very large olecranon process. 



There were five well-developed digits in the manus. The meta- 

 carpals are short and stout, with rvigose extremities. The distal 

 phalanges are broad and hoof-like, showing that the fore-feet were 

 distinctly ungulate (Woodcut, Figs. 11-16, pp. 245-246). 



The Pelvis. — The pelvis in this group is very characteristic, and 

 the three bones, ilium, ischium, and pubis, all take a prominent part 

 in forming the acetabulum. The relative size and position of these 

 are shown in the diagram (Woodcut, Fig. 4), which represents the 

 pelvic elements as nearly in the same plane as their form will 

 allow, while retaining essentially their relative position in life. 



The ilium is much elongated, and differs widely from that in any 

 of the known groups of the Dinosauria. The portion in front of 



^ Read before Section C, of the British Association for the Advancement of Science, 

 at the Leeds Meeting, September 4, 1890. See also American Journal of Science (3), 

 vol. xxxvi. p. 477, December, 1888 ; vol. xxxvii. p. 334, April, 1889; vol. xxxviii. 

 p. 173, August, 1889, p. 501, December, 1889; and vol. xxxix. p. 81, January, 

 1890, p. 418, May, 1890. 



DECADE ni. — VOL. VIII. ^NO. TI. 16 



