CHAP. IV] THE GENERAL ANATOMY OF THE TARSII 107 



The extraordinary elongation of the os calcis and os naviculare 

 has been noted already. The distal phalanges of the digits are 

 relatively very short. The nails on the second and third digits are 

 distinct from the remainder by reason of their spur-like form and 

 erect position. The fourth digit is the longest of all and in this 

 respect Tarsius resembles certain Frogs. 



F. Muscular System. In describing the more important 

 muscles, the same system is adopted here as was employed in the 

 case of the Lemur (v. supra, p. 77, footnote). 



1. The M. platysma is fully developed, but I am unable to 

 detect a M. sphincter colli in the specimen of Tarsius dissected. 

 The auricular muscles are large and prominent, being thus appro- 

 priate to the enormous ears. The M. dorso-humeralis is also very 

 distinct and extensive. So substantial is it, that it may be 

 mistaken for the M. latissimus dorsi, on which it lies. 



2. The M. digastricus is very different from that of the Lemur, 

 and approaches the human form of this muscle. A thin cord-like 

 tendon intervenes between the posterior belly (attached to the 

 occiput), and the anterior belly. The latter contains no tendinous 

 fibres where it is attached to the mandible, and it extends back- 

 wards from the symphysial region for a considerable distance. 

 Here it is applied to the lower border of the jaw, but is not over- 

 lapped by that bone. 



3. The M. sterno-mastoideus is wide and ribbon-like. In 

 origin it is entirely sternal, and the site of its attachment extends 

 above the presternum, the prolongation resembling that seen in 

 Pteropns (Cheiroptera). The M. cucullaris (trapezius) barely 

 extends to the occiput above, and its lower part is separated as a 

 M. depressor scapulae. Beneath this stratum the M. rhomboideus 

 is situated, as well as an aberrant slip named from its attachments 

 M. occipito-scapularis, though it lies deep to the M. trapezius and 

 may represent part of the M. levator anguli scapulae. 



4. The M. deltoideus does not extend so far towards the 

 vertebral border of the scapula as in Lemur, but this " spinous " 

 portion is distinct from the rest of the muscle. The M. pectoralis 

 major is entirely "sternal" in origin : at its caudal border it blends 



