Studies on Avian Anatomy. — II. 
25 
It crosses over the humeral head in front of the os humero-scapulare, 
and inserts tendinously on the tuberculum laterale of the humerus. 
Origin in Bubo (Del. m., PI. III., fig. 26; PI. IV., fig. 30) is from 
the clavicle facing surface of the coracoid and from the clavicle. 
Its fibres fuse with the underlying portion of the M. deltoideus major, 
coming from the foramen triosseum, but it lies mainly in front of 
that muscle. It crosses the humeral head in front of the os humero- 
scapulare and is inserted on the tuberculum laterale of the hum- 
erus, continuing down the crista lateralis to the insertion of the 
M. pars thoracica. Origin in Aeronautes (Del. m., PI. IV., fig. 56) 
the anterior one of the two bundles is from the coracoid facing sur- 
face of the scapula and the ligament coraco-scapulare dorsale. It in- 
serts at the base of the crista lateralis of the humerus, anterior to 
the tendon of the M. supra coracoideus. The origin of the posterior 
one is on the dorsal surface of the scapula immediately following 
the first. It inserts at the base of the crista lateralis of the humerus 
posterior to the tendon of the M. supra-coracoideus. Both bundles 
are almost covered by the M. deltoideus major, but with its fibres 
they do not fuse. 
3. M. latissimus dorsi. In all the birds this consists of two por- 
tions. 
M. latissimus dorsi anterior. Origin in Geococcyx (Lat. d. a., PI. 
II., figs. 15, 19) is fleshy on the posterior part of the first dorsal ver- 
tebra, second, third, and part of the fourth. It inserts by a thin 
tendon on the dorsal surface of the humerus at the base of the M. 
deltoideus major near the mid point of its insertion. Origin in 
Bilbo (Lat. d. a., PI. III., figs 26, 28; PI. IV., fig. 33) is on the 
second and the third dorsal vertebrae. It is inserted tendinously on 
the dorsal surface of the humerus at the base of the M. deltoideus 
major. Origin in Aeronautes (Lat. d. a., PI. VI., figs. 52, 54) is ten- 
dinous on the second, third, and part of the fourth dorsal vertebrae. 
It is inserted fleshily on the dorsal surface of the humerus at the 
base of the posterior bundle of the M. deltoideus minor. 
M. latissimus dorsi posterior. Origin in Geococyx (Lat. d. p., 
PI. II., figs. 15, 20) is semitendinous from dorsal vertebrae follow- 
ing the fourth and tendinously from the anterior border of the 
ilium. It is inserted semitendinously on the dorsal surface of the 
humerus between the short heads of the M. pars liumero-cubitalis at 
the beginning of their union. Origin in Bubo (Lat. d. p., PI. III., 
figs. 26, 28; PI. IV., fig. 33) is tendinous on the anterior border of 
the ilium, and has fascia connection with the M. rliomboideus super- 
ficialis. Its fibers are fused with those of the M. latissimus dorsi 
anterior as it passes under that muscle, but it emerges from under 
