REPORT ON THE SEALS. 161 



but I made it out as blending with the flexor minimi digiti. In Otaria it arises from the inferior 

 angle, but in Arctocephalus from the axillary border ; the fibres in the former run to the forearm, 

 but in the latter they blend with the flexor carpi ulnaris. Trichechus agrees with Arctocephalus 

 in the origin, but the insertion differs, for it ends in the antebrachial fascia of the forearm, and 

 is inserted into the olecranon by fascia only. 



The second, or long head of the triceps, 1 is a triangular muscle, and arises between the origin of 

 the teres minor anteriorly and the teres major posteriorly. The extent of its origin is from a spot 

 immediately posterior to and in a line with the middle of the scapular spine to the glenoid cavity ; 

 the portion arising from the scapula is thin and chiefly tendinous ; the remainder which arises from 

 the neck is muscular, and covers the under surface of the neck as well as the lower half of the back. 

 Tt also has origin from the capsule surrounding the neck. The lower half of this muscle lying next 

 the external head is tendinous ; it lies upon the internal and external heads, and is inserted into 

 the olecranon below the middle head, into both of its sides and into the tendinous surface on the 

 posterior of the external head. 



In Ardoceplmlus gazclla it is also triangular, and arises from the outer half of the dorsal rim of 

 the posterior costa of the scapula, between the fibres of the subscapularis, which springs from the 

 posterior costa, and posterior to the infraspinatus, which overlaps it. It stretches transversely 

 from above the middle of the posterior costa to the under surface of the capsule of the shoulder- 

 joint, from which it also has origin. The ventral surface is tendinous for the play of the teres 

 major, while the dorsal is only tendinous near the olecranon above its insertion. As in Phoca it lies 

 on the external and internal heads, when viewed from the inner aspect of the hmb ; and it is inserted 

 into the anterior internal half of the border of the olecranon on the inner surface, which is opposite 

 the anterior and middle tubercles of the outer surface ; some of the fibres run amongst those of 

 the internal head over the quadrilateral surface of the olecranon on the internal side, and it is 

 tendinous on the outer surface near the olecranon. In Otaria and Tricheelius it joins the common 

 cubital insertion of the triceps. 



The third or external head 2 arises from the capsule surrounding the head of the humerus, which 

 is continuous with the posterior surface of this bone, and from the same position on the outer 

 surface to midway between the anterior and outer borders, from the hollow between the head and 

 the shaft, and very slightly from the humerus below this. It overlies the internal head, and is 

 closely connected to the tendinous lower half of the long head which covers it : it then joins the 

 anterior tendinous side of the long head, and is inserted by a small fasciculus into the outer side of 

 the tip of the olecranon between the internal heads. 



In Arctocephalus gazclla it arises from the capsule of the shoulder-joint at the lower posterior 

 surface of the glenoid cavity; from the capsule between this and the neck of the humerus; from the 

 neck to the middle of the outer surface ; from the capsule above the neck, and also from the 

 external border of the shaft in its upper half. It has an opening, near its origin from the capsule 

 on the external border, for the circum3ex vessels. It divides above the olecranon into two parts ; 

 the inner is inserted into the tendinous portion of the long head above the olecranon and into the 

 inner side of the olecranon, opposite to the anterior and middle tubercles to the outer side of the 

 long head, and a slip from it joins the dorsi-epitrochlear ; the outer is inserted into the superior 



1 Tbis is Humphry's second division ; Lucae's middle head ; Murie's first division. 



2 This is Humphry's third division; Murie's (Trichechus and Otaria) second division. 



(ZOOL. CHALL. EXP. — PART LXVIII. — 1888.) Yyy 21 



