EEPOET ON THE SPHENISCIDJE. 89 



time that it elevates it. In this respect it is the direct antagonist of the latissimus 

 dorsi. 



Relations. — The muscle is in part subcutaneous, and rests upon the shoulder joint. 

 Its anterior margin lies in contact with the pectoralis major. Its posterior border is 

 concealed by the long head of the triceps. The tendon of insertion of this muscle 

 contributes, along with that of the pectoralis major, to the formation of the alar 

 aponeurotic sheath described along with the last-named muscle (see page 80). 



Nerve supply. — A branch from the trunk of the musculo-spiral. This branch winds 

 round the inner side of the neck of the humerus, and enters the posterior border of the 

 muscle. 



Variations. — In Pygosceles toBniatus, as well as in Aiotenodytes longirostris, the tensor 

 patagii longus is divisible into two portions — a superficial and a deep. The superficial 

 part (detoideus posterieur of Gervais and Alix, p. 23) arises from the dorsal, recurved 

 extremity of the clavicle, between the articulation of the latter with the coracoid and 

 with the scapula. It is inserted into the posterior margin of the humerus, immediately 

 above the insertions of the two tendons of the latissimus dorsi. The deeper portion of 

 the muscle corresponds exactly to the tensor patagii longus as above described, and is 

 inserted in a similar manner into the anterior or radial border of the humerus. 

 In Aptenodytes longirostris, moreover, there is an accessory slip to the tensor patagii, 

 the presence of which I could not substantiate in any other species of Penguin. It 

 arises from the outer surface of the sterno-clavicular aponeurosis, immediately in front 

 of the origin of the pectoralis medius, and passing through the foramen bounded by 

 the three bones forming the shoulder girdle, is inserted along with the deeper fibres 

 of the tensor patagii longus into the anterior or radial border of the humerus. 



Remarks. — Schoepss figures the tensor patagii longus in the Penguin as consisting 

 of two bellies, an anterior and a posterior. Gervais and Alix also describe in Eudyptes 

 chrysolophus a " deltolde j^osterieur," which evidently corresponds to the superficial 

 portion of the tensor patagii longus above referred to as occurring in Ai^tenodytes 

 longirostris and in Pygosceles tceniatus. Meckel describes the tensor longus in the 

 Penguins as consisting of two bellies, one of which can with difficulty be separated from 

 the pectoralis major. One of these evidently corresponds to the superficial, the other 

 to the dee2;)er portion of the tensor patagii longus above noticed as occurring in Ai^teno- 

 dytes and in Pygosceles. Possibly this is the normal arrangement in all species of 

 Penguin, although I failed to identify it in any excepting Aptenodytes and Pygosceles. 

 It must be remembered, however, that all the specimens examined had been sub- 

 mitted to the action of preservative fluids, which may have prevented the separation 

 and identification of two portions of this muscle in any but the two species above 

 mentioned. 



The accessory slip above described in Aptenodytes does not aj)pear to have been 



(ZOOL. CHALL. EXP. PART XVIII. 1883.) S 12 



