88 THE VOYAGE OF H.M.S. CHALLENGER. 



The fibrous pulley (PI. X. fig. 4) through which the two tendons of the latissimus 

 dorsi pass, consists of a ligamentous band which measures half an inch in length, and is 

 attached to the axillary margin of the scapula close to the glenoid fossa. The free 

 extremity of the band is perforated by the tendons in question, the aperture being lined 

 by a synovial membrane. 



Nerve supply. — A branch from the musculo-spii-al nerve, which divides into two 

 twigs — one to each portion of the muscle. 



Variations. — In Eudyptes chrysocome from Kerguelen, portion A. of the latissimus 

 dorsi arises from the spines of the last two cervical and first three dorsal vertebree. This 

 is also the case in Eudyptes chrysolophiis. In Splieniscus magellanicus the tendon of 

 insertion of portion A. is double, and this portion of the muscle arises from the spines of 

 all the dorsal vertebra except the last. In Splieniscus minor, Pygosceles tceniatus and 

 Aptenodytes longirostris the two portions of the latissimus dorsi are not separated by 

 an interval at their origins as in the other species, but form one continuous muscular sheet, 

 the fibres of which, however, end on two distinct tendons which are arranged precisely as 

 in all the other species examined. 



According to Meckel and Schoepss, in the Penguin the two portions of the latissimus 

 dorsi are united at their origins, as described above in Pygosceles. Meckel, moreover, 

 states that the anterior part of the muscle (portion A. of my description) is provided 

 with two tendons of insertion, as noticed above in S2jheniscus magellanicus. 



1 0. Musculus tensor patagii longus. 



Grand extenseur de la membrane de Vaile, Yicq d'Azyr, 1773, p. 568, No. 3. 



Der langamiige Muskel, Merrem, p. 156, No. 1. 



Spanner der vordei-en Fliigelliaut, Tiedemann, vol. ii. p. 317. 



Spanner der vorderen F/ugelhaut, Heusinger, p. 185, No. 19. 



Spanner der vorderen Flugelhaut, Wiedemann, p. 85, No. 2. 



Tenseur de la membrane anterieure dii vol, Meckel, vol. vi. p. 61. 



hanger MusM der vorderen Flugelfalte, Schoepss, p. 82, No. 2. 



Deltoid (]), Eeid, p. 141. 



Tensor patagii longus, Selenka, vol. vi. p. 122, No. 48. 



Tenseur marginal de la memhrane anterieure de Vaile, Gervais and Alix, p. 23. 



Attachments. — This muscle arises from a small part of the dorsally recurved portion 

 of the clavicle, from the hook-like extremity of the coracoid bone, and from the coraco- 

 clavicular ligament. The fibres converge as they pass backwards and outwards over the 

 shoulder joint, and are inserted by means of a tendon into the whole length of the 

 anterior or radial margin of the bones of the wing, as far as the extremity of the last 

 phalanx. 



Action. — The muscle carries the wing forwards at the shoulder joint, at the same 



