1897.] NEW YORK ACADEMY OF SCIENCES. 347 



Murie and Mivart describe in their specimen of Cheiromys one 

 large Supracostal muscle, arising from the cartilage of the third 

 rib close to the sternum and inserted into the first rib just ex- 

 ternal to the attachment of the Subclavius, and just over the ex- 

 ternal half of the insertion of the Rectus, the Scalenus lying 

 immediately to the outer side. 



Lucre neither describes nor figures the muscle in Lemur ma- 

 caco. 



The Supracostal muscle in Mammalia presents numerous vari- 

 ations as regards occurrence, extent, mode of origin and insertion, 

 and number. This variability is well shown by the differences 

 just quoted, which the muscle exhibits in the various genera of 

 Lemuroidea,as well as by the above detailed instances of its ab- 

 sence. 



Comparing the Lemurs with the remaining Mammalia on the 

 one hand, and with the higher Primates on the other, it becomes 

 apparent that the frequent occurrence of the muscle in the differ- 

 ent genera of the suborder is to be taken as an indication of the 

 transitional position occupied by the Lemurs, as intermediate 

 between the lower mammalian groups and the higher Primates. 



If we sum up our linowledge concerning the supracostal mus- 

 cle in tabular form the following results arc obtained. (See p. 

 348.) 



This by no means comprehensive review of the muscle in 

 mammalia shows that its occurrance is fairly constant in nearly 

 all orders until the Prosimians are reached. Here the muscle 

 becomes irregular in its arrangement, occasionally defaulting en- 

 tirely. In the cynomorphous monkeys among Primates it is 

 still encountered, at least in the instances examined. There is 

 great need of more extended investigation of this muscle in the 

 lower monkeys, the old world forms as well as the Hapalidae 

 and Cebidse, and I propose to pursue such investigation shortl}^ 

 on material sufficiently extensive to aff"ord conclusive results. 



In the Anthropomorpha and Man the muscle is absent, occur- 

 ring, however, at times as a rare variation in the latter. Undoubt- 

 edly the migration of the attachment of the Entopectoral from the 

 sternal line to the lateral surfaces of the ribs has played an im- 

 portant part in the displacement of the Supracostal muscle in 

 Man and the highest Apes, the Pectoral group actually occup}'- 

 ing the region usually assigned to the muscle in the lower forms. 

 A tendency to lateral recession of the caudal origin of the Ento- 

 pectoral has been noted above in Lemur hruneus^ and it is 

 possible that further investigations of the myology of the 03^0- 

 morpha, Arctopithecini and Platyrrhini will confirm the impres- 

 sion that the Supracostal muscle of the Lemuroidea represents 



