820 PEOF. I", a. PAESOisrs oif the 



Omo-liyoid. — This muscle I bave hitherto found in every 

 specimen of sciuromorphine and myomorpliine rodent which. I 

 have dissected, but it is absent in many of the Hystricomorpha 

 and in the Lagomorpha. In Anomalurus it is absent, and, if tbis 

 should prove constant, it will be a mark of distinction between 

 that animal and other sciuromorphine rodents. 



The Omo-trachelian {Levator claviculce) rises from the anterior 

 arch and transverse process of the atlas and is inserted into the 

 acromion and metacromion ; these are its usual attachments in 

 Sciuromorpha and Myomorpha, though in the Hystricomorpha 

 and Lagomorpha it often rises from the basioccipital. 



Rliomboidei. — The rhomboideus capitis in Anomalurus forms a 

 continuous sheet with tlie cervical and thoracic parts of the 

 muscle : this is generally the case in the Sciuromorpha, but in the 

 Myomorpha the rhomboideus capitis is usually a distinct muscle. 



Splenii. — The splenius capitis is always well developed in 

 rodents, and in Anomalurus it has the usual arrangement ; the 

 splenius colli, on the other hand, is a rare muscle, and Anomon 

 lurus differs from most other rodents in having it well marked. 



Trachelo-mastoid is present as in most rodents. 



Scaleni. — A scalene muscle passing ventral to the subclavian 

 artery and brachial plexus is never found in the Sciuromorpha, 

 very rarely in the Myomorpha, but often in the Hystricomorpha 

 and Lagomorpha. Anomalurus has no scalenus ventralis or 

 anticus,as this muscle is usually called ; it has, however, a scalenus 

 longus passing to the anterior four ribs and, dorsad to that, a 

 scalenus breads inserted into the first rib. 



Muscles of the Anterior Extremity. 

 The Pectoral Muscles. — I propose to adopt the same method 

 of dividing this group that I have found to work fairly well in 

 other rodents *. (a) The superficial manubrial fibres : these also 

 rise slightly from the clavicle and pass superficially to all the 

 other fibres to be inserted lowest of all, opposite the lower part 

 of the insertion of the deltoid. (/3) The greater portion of the 

 muscle rises from the whole length of the manubrium and gladi- 

 olus and passes, deep to the last, to be inserted into the pectoral 

 ridge. (7) The abdominal fibres, or Pectoralis quartus, rise from 

 the linea alba as far back as the umbilicus and are inserted into 



* P. Z. S. 1894, p. 259. 



