EOSIREN LIBTCA. 213 



haemai ridge ; the transverse processes or sacral ribs (s.r.) are very large, expanding 

 considerably towards their outer ends, which are truncated by a flat surface looking 

 downwards and outwards, probably for connection with the ilium. 



Several caudal vertebrae (PI. XX. fig. 5) are present. In these the anterior face of 

 the centrum is nearly as high as wide, while in the case of the posterior face the 

 width is the greatest. The neural arch and spine are low, and both anterior (a.z.) and 

 posterior zygapophyses well developed. The transverse processes are broad, short, 

 and somewhat downwardly directed. The posterior border of the ventral side of the 

 centrum bears a pair of facets for a chevron-bone. 



Fore Limb. — ^The scapula (PI. XX. fig. 3) is of a very primitive Sirenian type, and 

 very nearly resembles that of Halitherium (Prototherium) veronense figured by Zigno 

 (Mem. 1st. Veneto d. Sci. vol. xxi. (1880) pi. iv. fig. 1). The blade is strongly 

 curved backwards, the upper border being drawn out into a tongue-shaped prolongation. 

 In the middle the width is much greater than towards the ends, owing to the strong 

 convexity of the coracoid border {c.b.). The postscapular fossa is narrow and of nearly 

 uniform width throughout, the prescapular fossa is very wide, the subscapular surface 

 is quite flat. The spine [sp.) is low and dies away above some distance from the supra- 

 scapular border. Towards the lower end its base terminates about 2'5 cm. above the 

 glenoid cavity, while its upper border is produced into a short acromion process 

 directed downwards and backwards, but not reaching nearly to the level of the glenoid 

 cavity. The coracoid process {cor.) is fairly prominent, more so than in Halitherium 

 veronense, and its extremity is sharply truncated by a somewhat concave surface for 

 the attachment of a muscle. The glenoid cavity [gl.) is comparatively large ; it is oval 

 in outline and is produced somewhat forwards and downwards on to the base of the 

 coracoid prominence ; its direction is more oblique to the axis of the scapula than in 

 H. veronense. 



Comparison with the scapulae described and figured by Abel {op. cit. supra, 

 pp. 164-68, pi. ii.) shows that in its small size, in the narrowness and curvature 

 of the blade, in the small size of the coracoid process (larger, however, than in 

 H. veronense), in the approximation of the lower end of the spine to the glenoid cavity, 

 and in the form of the latter, this bone is primitive, as might be expected from the 

 age of the deposits in which it is found. 



The humerus is known only from a young specimen wanting the proximal 

 epiphyses, and from the very imperfect proximal and distal ends of adult bones. In 

 the most nearly complete specimen figured on PI. XX. fig. 7, both the greater 

 {q.t.) and lesser {l.t.) tuberosities are well developed, and there is a well-marked 

 bicipital groove {l.g). The deltoid crest {d.) is prominent and is continuous in the 

 middle of the shaft with a strong ridge which runs up to the inner angle of the 

 greater tuberosity. The trochlea {tr.) is somewhat oblique, and both the coronoid and 

 olecranon fossae are deep, though there is no supratrochlear perforation. The inner 



