subis._ Lateral view of left half of
thorax. _M. pectoralis thoracica_ (area of insertion indicated by dotted
line) has been removed. Muscles not described in text are not shown. (x
1.5.)]

[Illustration: FIG. 2. _Progne subis._ Lateral view of left half of
thorax. Same view as shown in Fig. 1, but with _Mm. supracoracoideus_,
_coracobrachialis posterior_, and _intercostales externus_ removed. (x
1.5.)]

[Illustration: FIG. 3. _Progne subis._ Medial view of left half of
thorax. Not all muscles shown. See Fig. 4 for identification of
arteries. (x 1.5.)]

[Illustration: FIG. 4. _Progne subis._ Lateral view of left half of
thorax. (x 1.5.)

(Applies also to Fig. 3.)

1. Subclavian artery.
2. Coracoid artery.
3. Thoracic artery.
4. (Unnamed.) Supplies _M. coracobrachialis posterior_.
5. (Unnamed.) Supplies _M. subcoracoideus_.
6. (Unnamed.) Supplies _M. sternocoracoideus_ and sternum.
7. (Unnamed.) Supplies _M. subcoracoideus_.
8. (Unnamed.) Supplies _M. sternocoracoideus_, _M. coracobrachialis
posterior_, and sternum.
9. Pectoral artery.
10. Axilliary artery.
11. (Unnamed.) Supplies _M. coracobrachialis posterior_.
12. (Unnamed.) Supplies _M. supracoracoideus_.
13. (Unnamed.) Supplies _M. costi-sternalis anterior_.
14. Carotid artery.]

[Illustration: FIG. 5. _Scardafella inca._ Lateral view of left half of
thorax. _M. pectoralis thoracica_ (area of insertion indicated by dotted
line) has been removed. Muscles not described in text are not shown. See
legend for Fig. 7 for identification of arteries. (x 1.)]

[Illustration: FIG. 6. _Scardafella inca._ Lateral view of left half of
thorax. See legend for Fig. 7 for identification of arteries. (x 1.)]

[Illustration: FIG. 7. _Scardafella inca._ Medial view of left half of
thorax. (x 1.)

KEY

(Applies also to Figs. 5 and 6.) Numerals not used are those used for
_Progne subis_ for which no homologous artery occurs in _Scardafella
inca_.

1. Subclavian artery.
2. Coracoid artery.
3. Thoracic artery.
4. (Unnamed.) Supplies _Mm. coracobrachialis posterior_ and
_sternocoracoideus_.
4a. (Unnamed.) Supplies _M. coracobrachialis posterior_.
6. Sternal artery. (Shown as it appears on _right_ side. Left sternal
artery not so extensive.)
6a. (Unnamed.) Supplies _M. sternocoracoideus_.
7. (Unnamed.) Supplies _M. subcoracoideus_.
8. (Unnamed.) Sup