958 THE OSTEOLOGY AND MYOLOGY OF THE DEATH ADDER, 

 M. COSTO-MANDIBULABIS. 



M. costo-mandibularis, Duvernoy, Jones and Owen / included in 

 the Cervico-hyoideus of Hoffmann and D'Alton. 



The costo-mandibularis is formed by plates of muscle which 

 spring from the costal cartilages of the third to the tenth rib. 

 These bundles correspond to those described as forming posteriorly 

 the internal oblique proper. Instead of being inserted into the 

 superior layer of the rectus, the bundles are collected into a sheet 

 which runs forward above the fibres of the depressor mandibulae, 

 and coalesces with them, helping to form the mylohyoid, at the 

 same time becoming inserted into the hyoid bone. 



In Daboia, however, where the tendinous intersections occur, 

 these bundles are inserted into the posterior tendinous band, and 

 thus represent a sternohyoid muscle. 



Hoflfmann has followed D'Alton in describing this muscle as 

 part of the depressor mandibulse, but from its formation and 

 relations, it clearly belongs to the middle and not to the external 

 stratum. 



From its insertion into the hyoid the muscle can act as a 

 retractor of the lingual sheath and tongue, thus resembling the 

 action of the sternohyoid. 



By its continuation into the mylohyoid, and so indirectly on to 

 the mandible, it can act as a depressor of the lower jaw. 



M. HYO-GLOSSUS. 



M. hyofflossus, Hoffmann, Owen ; Zungenbeinmuskel, D'Alton. 



The hyoglossi come into view when the mylohyoid is reflected. 

 The muscles arise as two rounded bellies from the inner side of 

 the ossified hyoid rods. Running forward the muscles coalesce, 

 and are continued as one muscle into the lingual sheath, where 

 they join the intrinsic muscles of the tongue. 



These muscles are generally taken to represent the hyoglossi, 

 but it is doubtful if this is their true homology. Owen is certainly 



