28 PROCEEDINGS OF THE ACADEMY OF 



Others, and the region around the foramen for the seventh pair is very rugose 

 and gives rise to a process behind the formen. The prootic is acuminate ante- 

 riorly, and ends in an acute process. The inner lip of the t^-mpanic is much 

 elevated at its anterior extremity, causing the protile of this extreme of the 

 bulla to be truncate instead of accuminate ; the Rustachian sinus is thus 

 shorter and broader. Of the longitudinal lobes of the inferior surface of the 

 bulla, the interior is weaker and the external more prominent and narrower 

 than in the de cli v is. The anterior end of the inferior view is broader, 

 more oblique, and more truncate than in the other species. 



angustata. declivis. rhinodon. Steno frontatus.* 



Length of tympanic bulla 1 in. 111. 1 10 1 9-^ 1 7-5 



" " other elements 2 3-5 1 11-5 1 10 1 4-5 



Total depth 2 1 8 1 7'5 1 3 



General 3Ieasurements. 



No. In. Lin. 



Cervical vertebrje 7 7 3 



Dorsal " 11 28 7 



Lumbar (to 1st chevron bone) 10 40 



Caudal (imperforate) 1 3 7 



Caudal (perforate) 18 31 9 



Caudal (from first wanting neural spine) (11) 



With cranium 22 



Total 11 ft. 1 in. 2 1. 133 2 



The cervical vertebrae are in general similar to those of B. angustata; 

 they present the same acute infero-posterior process of the atlas, short trun- 

 cate inferior lateral processes and longer but weak superior lateral. As in 

 it the last is longest and recurved to opposite the sixth. There is nowhere a 

 vertebral foramen. They differ from those of the a n g u s t a t a in the heavier 

 proportions of the atlas and axis, and the high compressed carinate neural 

 spine of the latter. The axis is also peculiar in that the inferior (circular) 

 surface of articulation with the atlas process occupies a median position of 

 the inferior face, and is separated by a deep groove from an anterior trans- 

 verse articular surface, which belongs to an apparently decurved odontoid 

 process. The latter fits a corresponding and separate surface just behind the 

 margin of the spinal canal of the atlas. 



Width of spinal canal above 2 8.5 



" " " below 1 8 



Transverse diameter of atlas 7 10-5 



Vertical " " 4 1 



Transverse diameter of axis 7 0-8 



" " of centrum of do 2 105 



Height of neural canal 1 8 



Length of neural spine (superiorly) 3 5 7 



The neural canal is rather depressed, and angulate above ; the arches of the 

 fourth and seventh are incompletely united above, and the latter has a trace 

 only of neural spine. Its dimensions are 



Length of body 11 



Transverse diameter of same 2 6-4 



" " " neural canal 2 9-5 



" extent of diapophysis from canal 1 11 



Heighth of neural canal 2 2 



The dorsal vertebrae are not so short as in the B. rh i n o d o n, and the neural 

 spines are low ; seven of them furnish an entire articular surface near their 

 posterior border for the ribs, commencing with the second pair. 



The lumbars are heavy, and have long diapophyses which are dilated dis- 



* From specimens described in Proc. Acad., Phila., 18G5, p. 204. 



[April, 



