THE RIGHT WHALE OF THE NORTH ATLANTIC. 921 
The skull of biscayensts was in breadth about two-thirds of its length, that of 
mysticetus about one-half. In biscayensis the height and breadth of the occipital 
squama approximated, in mysticetus the breadth was materially greater than the height, 
and the posterior surface of the squama differed in character in the two species. 
The fronto-orbital diameter was broader than the squamoso-occipital in biscayensis, 
whilst in mysticetus they were about equal. The nasals in biscayensis were broader _ 
relatively to the length, and their posterior border was almost transverse, whilst in 
mysticetus two processes from the frontal passed between them. The anterior nares 
were also broader in biscayensis than in mysticetus. 
The tympanic bones were very distinctive, the most noticeable features being the 
presence in bescayensis of a deep notch on the outer surface behind the lip-like process, 
and a much deeper notch at the anterior or Hustachian end of the upper border of the 
inner surface than in mysticetus. 
The vertebral formula in biscayensis was C,D,,L,,Cd,,=56; in mysticetus 
C,D,;L,,Cd.,=55, the important difference being the additional dorsal vertebra 
in the former, which is associated with the presence in it of 14 pairs of ribs, whilst 
mysticetus has only 13 pairs. 
The sternum was notched at its base, or anterior border, more deeply in some 
specimens of biscayensis than in others, whilst in mystecetus the notch, when sometimes 
present, was shallow. 
The scapula had only a rudimentary coracoid in biscayensis, whilst in mysticetus it 
was a distinct process. 
The ulna in biscayensis did not possess so prominent an olecranon process as in 
mysticetus. 
The manus corresponded generally in both species. The carpal elements were so 
imperfectly ossified in biscayensis that only two bones were present in one carpus, 
whilst the other had only a single bone. Notwithstanding the imperfect ossification 
the division of the cartilage into more or less definite areas was recognised, the 
customary three elements formed along with the pisiform the proximal row, and four 
_ apparently were in the distal row. In mysticetus four carpal elements and a pisiform 
have been described, but observations are still needed to enable a full comparison with 
biscayensis to be made. 
The pelvic bones resembled those in mystecetus, though they were not so thick as 
in that species and were somewhat more curved. Both species possessed a rudimentary 
osseous femur and a cartilaginous tibia. 
TRANS. ROY SOC. EDIN., VOL. XLVIII. PART IV. (NO. 33). 136 
