ANATOMY OF BALDEN O PTERA EOSTEATA. 
217 
which was about 3 inches long by 1^ inch in breadth on its outside. The glenoid 
cavity was shallow, rough, and ovoid in outline, with its larger extremity towards the 
external edge, straighter along the subscapular than the dorsal border ; its margins 
were rounded and covered with fibro cartilage. Anteriorly this cavity was bounded by 
a blunt coracoid eminence f of an inch long, tipped with cartilage, which received the 
insertion of the suprascapular ligament. In structure this bone was cancellous and soft 
towards the superior border, and denser towards the glenoid cavity. 
The humerus was a flattened irregularly club-shaped bone ; its head, roughly rounded, 
was united to its shaft by cartilage, its area being much greater than that of the glenoid 
cavity, and its long axis lying in the antero-posterior direction. The shaft was com- 
pressed in front and convex behind, presenting several rough facets for muscular attach- 
ments ; in those on the posterior surface were inserted the supraspinatus, infraspinatus, 
and deltoid above, the first occupying the most external position, the second placed inter- 
nally, and the third below and intermediate. From the posterior border of this surface 
the external head of the triceps arose, and lower down on the shaft the humerus was 
slightly hollowed to give origin to the extensor digitorum communis. The anterior 
surface presented internally a tubercle for the subscapularis, behind which extended an 
obscure ridge for the teres major ; above and externally the humeromastoid was inserted. 
The lower extremity presented two elliptical articular surfaces, so placed as to produce 
an obtuse angle with each other, the radial or larger surface looking downwards and 
outwards, the ulnar upwards and inwards. These surfaces were not covered by synovial 
membrane, as described in B. mysticetus by Eschricht and Reinhardt. 
The radius was a flattened, curved, elongated bone ; its humeral head was oval, with 
its long axis placed transversely ; the lower extremity was slightly dilated to correspond 
with the carpal bones. 
The ulna was likewise an elongated slightly curved bone, flattish, and separated from 
the radius by a small interosseous space. These bones at the proximal and distal 
extremities were in contact, and connected in the recent state by fibrocartilage. 
The humeral extremity of the ulna was larger than its carpal, and presented a promi- 
nence on its internal side, the olecranon process, which in the recent state supported 
a large triangular mass of cartilage from which the three flexor muscles arose, and into 
which the triceps was inserted. 
Of the carpal bones there were only four perfectly ossified, and in shape these were 
spherical, varying in diameter from ^ to a £ of an inch. The metacarpals were four in 
number, and ranged from 1 to 1-g- inch in length, the second being the longest. The 
phalanges were, as well as could be ascertained, four in each of the central digits, and 
three in each of the lateral ones. 
Eschricht and other authors have enumerated a larger number of phalanges as 
belonging to individuals of this species, but as in the present specimen the terminal 
extremities of the digits were purely cartilaginous, it was difficult to determine the 
precise number of rudimentary phalanges in each. According to Lilueborg the typical 
mdccclxyiii. 2 I 
