346 TRANSACTIONS OF THE [OCT. 4» 



4. M. SUPRACOSTALIS. 



(PL XXVIII. and XXXIY.) 



Origin: First rib, lateral surface and caudal border, ventrad 

 and caudad of attachment of Scalenus. 



Insertion : J^y a thin, strong tendinous lamina, closely con- 

 nected with the origin of the Entopectoral, some fibres of which 

 arise from it, into the sternum opposite the middle of the sec- 

 ond intercostal space, and into the cartilages of the third, fourth 

 and fifth ribs close to the sternum. The muscle crosses obliquely 

 over the subjacent upper prolongation of the Rectus muscle, 

 which reaches to the first rib. 



Murie and Mivart (1, p. 50) describe two small but very dis- 

 tinct muscles in L. catta, situated on each side of the thorax, 

 " between the long insertion of the Scaleni and the origin of the 

 Pectorals, but superficial to the intercostal muscles."' " The 

 first Supracostal muscle in L. catfa arises by tendinous fibres 

 from the cartilages of the fourth, fifth, sixth and seventh ribs, 

 and is inserted into the first rib, just external to the origin of 

 the Subclavius, crossing over the anterior end of the Rectus. 

 The second Supracostal muscle in the same animal arises from 

 the fourth and fifth digitations of the Serratus magnus. It is 

 inserted by a distinct and delicate tendon into the first rib." 



Van Campen (3, p. 27, PI. II., fig. 10) describes and figures the 

 same muscle in Ferodiclicus. Cuvier (11, PI. LXIX., fig. 2, 18) 

 figures a single but very large Supracostal muscle in L. varius, 

 under the name of Sterno-costal. Murie and Mivart (1, p. 51) 

 found the muscle absent in their specimen of L. varius, and, if 

 at all present, not distinct in L. nigrifrons. 



The same authors found the same muscle as described in L. 

 catta present in L. xanthomystax^ with nearly the same attach- 

 ments. They are doubtful about the representative of the 

 second Supracostal muscle in this animal. They found a second 

 small slip on the right side only, but consider it possible that 

 this was merely a portion of the sternal prolongation of the 

 Rectus muscle, as it lay rather to the inner side. 



In Galago crassicaudatus and G. allenii the same authors 

 found only a few fibres passing forward and outward over the 

 anterior prolongation of the Rectus from the third to the first 

 rib ; they consider this slip as corresponding to the first Supra- 

 costal muscle of Lemur catta. 



In Nijclicehus tardigradus Murie and Mivart describe a Supra- 

 costal muscle as passing from the third to the first rib. 



Burmeister does not mention the muscle in Tarsixis spectrum, 

 nor Allen in T. fuse us, or Owen in Cheironigs. 



