100 Prof. 0. C. Marsh — A Neio American Jurassic Dinosaur. 



Diplodocus, a study of which, more especially of the skull, throws 

 light on the whole group of Dinosaurian reptiles. 



Fig. 1. — Skull of Biplodoeus longiis, Marsh (one-sixth nat. size. Side view). 



The Skull. — The skull of Biplodoeus is of moderate size. The 

 posterior region is elevated, and narrow. The facial portion is elongate, 

 and the anterior part expanded transversely. The nasal opening is at 

 the apes of the cranium, which from this point slopes backward to 

 the occiput. In front of this aperture, the elongated face slopes 

 gradually downward to the end of muzzle, as represented in Pigure 1. 



Seen from the side, the skull of Diplodocus shows five openings : a 

 small oval aperture in front (a), a large antorbital vacuity {h), the 



Pig. 2. — Diagram of the stuU and hrain-cast of D. longus ; seen from above, one- 

 sixth natural size ; a, aperture in maxillary ; b, antorbital opening ; c, nasal 

 opening ; c, cerebral hemisphere ; d, orbit ; e, lower temporal fossa ; /, frontal 

 bone ; /', fontanelle ; m, maxillary bone ; m, medulla ; n, nasal bone ; oc, 

 occipital condyle ; ol, olfactory lobes ; op, optic lobe ; p, parietal bone ; pf, 

 pre-frontal bone; pm, pre-raaxillary bone; q, quadrate bone; qj, quadrate - 

 jugal bone ; I, lachrymal bone. 



