292 APPENDIX. 



inch above the foramen magnum, the broad arch of the tentorium, as long in its axial diameter as 

 the septum, extends on each side a little farther than the upper exterior angles of the condyles, 

 thence giving out a triangular wing on each side, -u-hich, attenuating as it descends, reaches the 

 floor of the brain cavity in advance of the opening betvs'een the alisialienoid and ex-occiijital, and 

 is ankylosed with the former. The cerebellar fossa is thus almost completely inclosed, communi- 

 cating with the cerebral fossa only by an 023ening in the front of the arch but little larger than 

 the foramen magnum, and by the narrow ojDenings between the outer edges of the wings of the 

 tentorium, bounded below by the alisphenoid, and laterally by the ex-occipital wall. The septum 

 ceases abrviptly in front, below the frontal and supra -occipital suture. A ridge from the front of 

 the tentorial wings is coossified with the orbito- sphenoid, above the sphenoidal fissure; the latter 

 in this species being posterior to and distinct from the foramen rotundum, which opens into the 

 cerebral cavity. 



In No. 2, the dimensions were constantly smaller, the skull belonging to a j'ounger, though 

 fully adult individual. The teeth were #1-,, the tip of the lower jaws being mutilated. The ten- 

 torium presented the same features as in No. 1, and the skull offered no sj^ecial peculiarities not 

 common to the other. 



The scapula and cervical vertebrffi of a third specimen, of which the entire skeleton was 

 preserved, offered the following peculiarities : The external face of the scapula is flattened, slightly 

 excavated in the middle, and with a slight ridge behind. The ^jrescapular fossa is inconspicuous, 

 but has a width of three - c[uarters of an inch on the outer face of the scapula, above the acromion. 

 The latter is tn shaped, notched above behind, with a projecting process below in front. The 

 upper anterior corner is connected with the anterior angle of the prescapular fossa bv a stronw 

 ligament; the anterior termination of the acromion is incurved, and externally convex. The cora- 

 coid is triangular, with the distal edge thickened, anteriorly excavated, and knobbed at the corners. 

 The external surface is concave. The glenoid cavity is sub-rotundate ; the piost-scajDular ed"e is 

 evenly rounded in a sigmoid curve. Beyond the upper posterior corner a triangular mass of 

 cartilage extends beyond the bone, an inch in its greatest width. The inner face of the scapula 

 is flattened, with three or four narrow low ridges radiating from the glenoid border. The inner 

 surface of the coracoid is convex, and of the acromion concave. The measurements are as follow 

 in inches and decimals : 



Greatest length of scapula 9 .50 



Greatest length of acromion 3 qq 



Greatest length of coracoid 2 . 25 



Greatest dianaeter of glenoid cavity \ 30 



Glenoid cavity to anterior angle 6 .25 



Glenoid cavity to superior border g qO 



Glenoid cavity to posterior angle g qO 



Glenoid cavity to anterior angle of acromion ^ go 



Glenoid cavity to anterior angle of coracoid 3 qo 



Glenoid cavity to posterior angle of coracoid 2 00 



The cervical vertebrae offer some difi"erences from those of Delphinus Bairdii. The atlas and 

 axis are solidly coossified by both body and spines ; the others are all free, thouo-h whether in 

 aged individuals this condition continues, is a matter of doubt. It is probable, from the "enerallv 

 abnormal condition of the cervical vertebrise in the Cetacea, that comparatively wide variations in 

 the amount of ankylosis may obtain in different individuals of the same species, and also in the 

 same individual at different ages. The bones in this individual are larger and stron"-er than in 

 D. Bairdii, but the spinal canal is proportionately smaller. The canal of the first spinal nerve 

 which in D. Bairdii is a shallow groove behind the upper edge of the condylar facets, is here (by 

 a slender process extending upward and backward from that edge, and coalescing with the anterior 

 base of the spinous process) converted into a foramen. The spine is keeled and convex below 

 instead of excavated, and flat, with a very narrow median keel, above. The spine is broader and 



