BY W. J. McKAY. 955 



In Acanthophis and the other venomous snakes examined, the 

 band was not so well developed as in Morelia. 



Retractor oris. 



detractor oris, Humphry ; Gervico-angular, Duvernoy ; M. 

 cervico - mandibulm^is (sphincter colli), Hoffmann ; Trachelo- 

 mastoideuSy Owen ; NackenunterkieferTnuskely D' Alton ; M. 

 temporalis, von Teutleben ; M. cervico-mandihularis, Cuvier. 



The retractor oris arises from the aponeurosis of the spinalis 

 attached to the anterior three or four neural spines. Running- 

 forward, outwards, and downwards, over the digastric and posterior 

 portion of the articular, the muscle ends in a tendinous expansion 

 inserted into the symphysis of the lips and the integument adjoining. 

 In Dahoia and Morelia this muscle divides into two layers as 

 it runs forward, the deeper one being inserted into the articular, 

 the superficial having the same arrangement as in Acanthophis. 



The muscle may represent a zygomaticus major. It certainly 

 corresponds to the retractor portion of the cervicalis superficialis 

 of Lepidosiren and the dogfish, as pointed out by Humphry. On 

 the other hand, it corresponds to part of the sphincter colli of 

 birds. 



The muscle acts as a tensor of the symphysis of the lips, thus 

 enabling the inferior portion of the masseter to work with a 

 " pully-like" action round the symphysis. Some of its fibres also 

 pass on to the capsule of the venom gland, thus serving to steady 

 the gland when the masseter is contracting on it. 



M. RETRACTOR OSSI QUADRATI. 



M. retractor ossi quadrati, Hoffmann; Riichwdrtszieher des 

 quadratum, D'Alton ; Filum musculare s.-tendinosum (?), Hiibner. 



This small band of muscle springs by a very delicate tendon 

 from the posterior portion of the upper extremity of the quadrate. 

 Running backwards and downwards the tendon gives way to a 

 muscle which passes beneath the retractor oris but lies on the 



