The appendi ciliar muscles of Xecturus niaculosns. 395 



The homologising of this muscle , which with soroe Variation is & 

 fairly constant one in urodeles, has caused much trouble. Hoffmann, in 

 his careful summary of amphibian muscles, names the ventral mass of 

 myotomic muscles lying between the sternal rudiments and the hyobranchial 

 apparatus the "thoracicohyoideus" and treats these slips as auxiliary fibers, 

 in which he and others are inclined to see the equivalent of the omo- 

 hyoideus. Deüner does not find a separate omohyoideus, or, as he prefers 

 to call it, a "pectori-scapularis", in either Necturus or Proteus, but thinks 

 that in spite of the difference of insertion, the omohyoid elements may 

 be found somewhere in these slips. Although in his description of this 

 muscle in Xecturus he says of the two slips arising from myocomma S 

 that "ihr Ansatz unterscheidet sich so sehr wesentlich von dem des M. 

 omo-hyoideus" (p. 606) under Proteus he wishes to see some connection 

 between the two. "Da ein M. omohyoideus (pectori-scapularis) bei Proteus 

 fehlt, liegt der Gedanke nahe, diese Muskeln, deren Verlauf und Habitus 

 eine gewisse Ähnlichkeit mit jenem nicht verkennen läßt, mit ihm in Ver- 

 bindung zu bringen" (p. 591). 



M. anconeus (= trieeps). This muscle oecupies the entire 

 dorsal or extensor surface of the humerus and is the homolog of 

 the muscle found in the same locality in all tetrapod vertebrates, 

 and usually called the "trieeps" from the name given to it in Man, 

 where it normally has three heads. In all cases the muscle arises 

 from several points of origin, and is thus composed of several slips, 

 which unite distally to form a stout tendon that inserts into the 

 olecranon process of the ulna. 



In Necturus there are four heads, as follows: 

 anconeus scapularis (as), 

 anconeus humeralis lateralis (aM), 

 anconeus humeralis medialis (ahm), 

 anconeus coraeoideus (ac). 



Of these the two flrst are visible superflcially from the lateral 

 aspect, the first and the fourth from the medial aspect, while the 

 third, which is the largest and deepest, is covered by the others.. 

 They may now be taken up in order: 



anconeus scapularis (as). This muscle forms the dorsal 

 (extensor) contour of the upper arm. It is a large muscle, the 

 proximal half forming a rounded belly, while the distal half be- 

 comes flattened towards the olecranon. It arises from the antero- 

 lateral lip of the glenoid fossa by means of a broad, firm ligament, 

 that serves as a portion of the capsular ligament of the Shoulder 

 Joint, The latissimus dorsi inserts by a tendon into the same liga- 

 ment, and thus the origin of the former and the insertion of the 



