342 TRANSACTIONS OF THE [OCT. 4, 



In regard to this muscle, therefore, Lemur hruneus ofters a 

 more advanced condition, compared with the remaining Lennir- 

 oidea. Whereas in these latter the cutaneous muscular panicu- 

 lus in the thoracic and axillar3^ regions presents still the ar- 

 rangement found in many of the lower mammalia, the axillary' 

 slip from Latissimus dorsi in Lemur hruneus marks the reduc- 

 tion of the muscular cutaneous bundles, and the more complete 

 and definite separation of Ectopectoral and Latissimus, all con- 

 ditions which are characteristically developed in the higher 

 Primates, and which appear in man as a distinct series of mus- 

 cular variations in the lateral thoracic, axillary and internal 

 brachial regions. 



2. The union of the abdominal division of the Ectopectoral 

 at the insertion with the tendon of the Entopectoral has also not 

 been described before in any of the memoirs on the various 

 genera and species of the sub-order. This arrangement again is 

 a strong indication of Simian affinity. In nearly all the lower 

 monkeys the abdominal Pectoral slip unites more or less com- 

 pletely' with the Entopectoral, either in the axilla or at the in- 

 sertion into the humerus. 



It is only necessary to refer in this connection to the corre- 

 sponding muscular variation in man, where the caudal Pectoral 

 fibres — representing the Abdominal Pectoral — either follow, as 

 M. Chondro-coracoideus, the Entopectoral to its secondar}' at- 

 tachment to the coracoid process, or, as M. Chondro-humeralis, 

 preserve their original direction and expand into the deep brach- 

 ial fascia over the Coraco-brachialis and short head of the Biceps. 



3. The folding of the sternal portion of the Ectopectoral at 

 the humeral insertion has apparently not been noted before in 

 any of the Lemuroidea. Allen (13, p. 42) states distinctly in re- 

 gard to the muscle in Tarsius fusciis ih^V' the sheet is not folded." 



The arrangement presented by the muscle in Lemur hruneus 

 reproduces exactly the disposition of the sterno-costal portion 

 of the Ectopectoral at the insertion in Man and the higher Pri- 

 mates generall}'. This folding of the Ectopectoral tendon of 

 insertion is in direct relation to the diminished extent of 

 brachial attachment which is to be observed in tracing the 

 muscle from the lower to the higher forms. 



Whereas in many of the lower Mammalia (Dasyjnis, Tatusia, 

 Phoca, Felidae, etc.) the Pectoralis has an extensive humeral at- 

 tachment, as well as a fascial insertion into the aponeurosis of 

 the arm and forearm, we find a marked regression of the inser- 

 tion among Primates, the muscle travelling cephalad toward tlie 

 proximal extremity of the humerus. That this process is not 

 associated with a reduction of the mass of muscular fibres as a 



