346 SCOTT. [Vol. V. 



In other respects it is not necessary to distinguish between the 

 two. 



Examining the skull more in detail, the following structures 

 present themselves. The basi-occipital is broader and flatter 

 than in Tragulus and tapers more regularly forward ; in the 

 chevrotains the enormous size of the tympanic bullae reduces 

 the basi-occipital and basi-sphenoid to a mere rod, which is 

 keeled in the median line. In Lcptomeryx this keel is not 

 present, but we find a pair of small surfaces for muscular attach- 

 ments, much as in the deer. The condyles are small, sessile, 

 and less widely separated than in the tragulines. The exoccipi- 

 tals are low and rather narrow, and are flat or even concave 

 from side to side, in sharp contrast to the very convex surface 

 of the smaller tragulines. The supra-occipital is, in one type 

 of Leptomeryx skull, quite high ; in the other much lower ; in 

 both it extends well over upon the sides of the cranial cavity 

 and is terminated by a projection which is the hindermost part 

 of the skull, whereas in Tragulus the upper margin of the fora- 

 men magnum projects further back. The lambdoidal crest is 

 much more prominent than in the tragulines. The foramen 

 magnum is also higher and somewhat narrower than in the 

 latter. The paroccipital processes are small, but are relatively 

 longer, stouter, and less compressed than in Tragulus; they 

 stand but very little in advance of the condyles, from which 

 they are separated by deep but narrow fossae. 



The basi-sphenoid is broader than in Tragulus, but does not 

 extend so far forward between the pterygoids. The alisphenoid 

 is directed nearly horizontally, but there is a curious angulation 

 or ridge in it, from which a portion of the bone passes upward, 

 bounding the anterior edge of the temporo-sphenoidal lobe of 

 the cerebrum ; the pterygoid plates of the alisphenoids are, 

 unfortunately, broken away in all of the specimens. The hori- 

 zontal portion is much longer than in the tragulines and much 

 more distinctly separated from the glenoid cavity. The orbito- 

 sphenoids are much as in the tragulines, and form a thin and 

 fragile interorbital septum. 



The tympanic bullae differ from those of the tragulines in a 

 very important and characteristic way ; they are very much 

 smaller in every dimension, but especially in the vertical direc- 

 tion ; they are not filled with cancellated tissue, but are hollow, 



