REPORT ON THE SEALS. 25 



cartilaginous division of the rib was long in relation to the osseous part, and in the 1st 

 rib it was as 87 mm. to 52 mm. The osseous parts of the ribs increased in length 

 from the 1st to the 8th, then they were almost equal in length to the 13th, whdst the 

 14th and 15th again were shorter. The last two ribs had no tubercles, and in the 13th 

 the tubercle was rudimentary. 



Sternum. — This bone was narrow and elongated, 468 mm. long ; it consisted of 

 ten segments ; all the bony segments were quadrilateral in shape, except the 8th, which 

 was a flattened disc. The first bony segment was more elongated than the others. 

 The margins of articulation of the bony segments consisted of unossified cartilages, and 

 at least one pair of costal cartilages articulated with the side of the sternum where the 

 segments were jointed together ; but between the 8th and 9th bony segments both the 

 9th and 10th pairs of cartilages articulated with the bone. The most anterior or prse- 

 sternal segment was a slender mesial cartilage of almost uniform transverse diameter 

 throughout, and 70 mm. long ; it projected forwards into the neck, and the 1st pair of 

 costal cartilages was articulated at the junction of this praesternal cartilage with the 1st 

 osseous segment. The last or xiphisternal segment was prolonged behind the last pah* 

 of sternal ribs ; its most anterior half was an elongated bone 50 mm. long, which was 

 continuous behind with a broad platedike cartilaginous xiphisternum. 



Anterior Extremity. — The scapula was falciform and 135 mm. in length. The 

 pras- and post-spinous fossae were almost of equal size. The upper two-thirds of the 

 spine formed so low a ridge as scarcely to be recognisable, the lower third, which was 

 32 mm. long, projected for 17 mm. from the dorsum of the bone. There was no 

 acromion and the coracoid was feeble. 



The humerus had a prominent deltoid ridge, inner and outer tuberosities about 

 equal in size, bicipital groove deep, no supra-condyloid foramen, capitellum and trochlea 

 both distinct. It was 117 mm. lon^. 



The ulna had a large olecranon ; its shaft was traversed by a strong anterior ridge 

 to which the internal lateral ligament of the elbow was attached ; its lower end was 

 somewhat rounded, and articulated with radius, cuneiform, and pisiform. It was 

 136 mm. long. 



The radius had a cup-shaped head, below which was a feeble bicipital tuberosity. 

 The shaft was rounded above and flattened out at the lower end, which articulated 

 below with a large scapholunar bone, and at its inner border with the cuneiform and 

 ulna. Its length was 126 mm. 



The manus was pentadactylous. Owing to the coalescence of the scaphoid and 

 lunare there were only seven carpal bones, which were rough both on the palmar and 

 dorsal surfaces for the attachment of ligaments, and which were devoid of ridges and 

 processes. The scapholunar articulated with radius, trapezium, trapezoid, os magnum, 

 and unciform. The cuneiform articulated with radius, ulna, pisiform, unciform, and 5th 



(zool. chall. exp. —tart Lxvin. — 1887.) Yyy 4 



