M. subcoracoideus (ventral head), Figs. 2 and 3. The origin is from the dorsomedial edge of the coracoid at its extreme proximal end, and to a slight extent from the adjacent portion of the manubrium. The origin is medial to the insertion of M. sternocoracoideus. The ventral head passes anterodorsally along the medial edge of the coracoid and joins the dorsal head (not here described). The combined muscle then inserts by a tendon onto the internal tuberosity of the humerus.
M. costi-sternalis, Figs. 1, 2, and 3. The origin is from the anterior edge of the sternal portion of the first four thoracic ribs. This triangular muscle narrows and inserts on the posterior edge of the apex of the costal process. The portion arising from the first rib may share slips with M. sternocoracoideus.
M. costi-sternalis anterior, Figs. 1, 2, and 3. This muscle is variously developed, and originates from a small area on the ventral end of the vertebral portion of the last cervical rib. The insertion is on the apex of the costal process, immediately anterior to the insertion of M. costi-sternalis.
Mm. intercostales externus, Fig. 1. These muscles extend posteroventrally between the vertebral portions of successive thoracic ribs, and between the last cervical and first thoracic ribs. In the more posterior intercostal spaces these muscles are poorly developed, but they become progressively better developed anteriorly, and are fully represented in the most anterior intercostal spaces.
Mm. intercostales internus, Fig. 3. These muscles resemble the external intercostal muscles, but extend anteroventrally, with the muscles being most fully developed posteriorly, and progressively less so anteriorly.
Costopulmonary muscles, Fig. 3. This diagonal series of muscle slips from the thoracic ribs attaches to the aponeurosis covering the lungs.
Angiology
Figs. 3 and 4 show all arteries discussed for this family. The numbers following the names or descriptions of arteries in the text refer to numbered arteries in one or both of these figures.
The right and left innominate or brachiocephalic arteries arise from the aortic trunk and give rise to the common carotid arteries (14). The major vessel continuing across the thoracic cavity is the subclavian artery. Classically the subclavian is considered as continuing into the anterior appendage as the axillary artery. However, in the species studied, the axillary artery can best be described as a branch from the subclavian; the pectoral stem forms a more direct continuation of the subclavian. In traversing the thoracic cavity, the subclavian gives rise to the thoracic, coracoid, and axillary arteries, and leaves the thoracic cavity as the pectoral trunk, dorsal to the area where Mm. coracobrachialis posterior and sternocoracoideus span the angle formed by the coracoid and costal process.
The pectoral trunk bifurcates into two main pectoral arteries (9), which penetrate M. pectoralis thoracica. Neither the axillary artery nor these pectoral arteries were traced in my study.