156 DE. J. MURIE ON THE FORM AND STEUCTUEE OF THE MANATEE. 



superficial to it, a slight portion of the pectoralis major only covering its inner edge 

 behind the pectoralis minor. The muscle in question occupies the inner half of the 

 abdomen (in the female specimen being four inches across) between the linea alba 

 and the cartilage-tipped rib-extremities ; and posterior to the pectoral muscles, or 

 from the fifth rib, it is overlain on its outer border by the tendinous fibres of the 

 external and internal oblique muscles. Posteriorly it is inserted into the cleft of the 

 pelvic bone by a thickened pyramidal point. 



The rete mirabile derivative from the internal mammary artery lies underneath the 

 rectus abdominis, as shall be described with the vascular system. 



2. Muscles of the Accessory Skeleton. 



(A) Those of the Shoulder-girdle. — The siqjra- and infrasinnatus are each long, 

 narrow, and thick ; they are of about equal size. The former is inserted broadly and 

 muscularly into the summit and front of the head of the humerus ; the latter, 

 narrower, rounder, and more tendinous, is implanted on the outer tuberosity. 



The subscapularis occupies the whole of the subscapular fossa excepting the space 

 where the serratus magnus and the rhomboideus are fixed. It is entirely fleshy, and 

 overlaps the lower border of the bone. A short, but strong, tendon forms its insertion 

 into the inner tuberosity of the humerus. 



The fleshy and strong teres major has origin from the lower dorsal edge and border 

 of the scapula, posterior to the spine. In close union with the latissimus dorsi it is 

 inserted into the inner aspect of the middle of the shaft of the humerus. The 

 latissimus partly overlaps the teres; and besides the approximation of these fibres, 

 there is a distinct fleshy slip which passes from the upper border of the former and 

 penetrates the latter close to where the tendon of insertion commences. 



No teres minor was observed. 



A single plane of broad, but short, muscular fibres, and but little tendon, the 

 rhomboideus, arises from the inner surface and vertebral border of the scapula, and 

 extends for an inch or more over the inner surface of the serratus ; it forms a shallow, 

 wide muscular arch spread over the sacro-lumbalis and below the posterior end of the 

 limited trapezius. 



A tra2>ezius is present in the Manatee, the muscular portion of which is in some 

 degree circumscribed ; for although broad and fan-shaped, the shortness of the neck 

 reduces it anteriorly. The fleshy part is attached the whole length of the spine and 

 dorsum of the scapula and the acromion process ; therefrom it radiates, and peripherally 

 is bounded by fascia which, with less distinct aponeurotic fibres than commonly 

 obtains in mammals, is lost in that of the dorsal region above and behind the scapula. 

 It is thickest and most muscular in the neck, and is fastened to the occiput. 



As in Cetacea, notwithstanding the shortness of the neck, a broad, moderately thick, 

 but powerful muscle, homologous ^vith the so-called cephalo-humeral, is present in the 



