916 THE OSTEOLOGY AND MYOLOGY OF THE DEATH ADDER, 



of the tongue. They end at about an inch from the symphysis of 

 the mandibles by converging towards the mid-line, and then 

 coalescing below the tongue. They are hidden from view by 

 the costo-mandibular muscles attached to their inferior surfaces, 

 while the mylohyoid arises from them anteriorly, and the hyoglossi 

 are attached along their internal borders. The genio-hyoglossi 

 are inserted into their anterior portions, and the hyo-trachealis 

 arises from the same region. 



The length of the bars varies in the various species examined, 

 being about IJ inch in Acanthophis, but about 3 inches in both 

 Pseudechis and Diemenia, so that the hyoglossi in these species 

 do not arise from the whole length of the bones, but only from 

 the anterior half, while posteriorly there is a special interhyal 

 muscle developed. These bars are taken by previous writers to 

 represent the ceratohyals of other groups. 



In Daboia, and, to a less degree, in Acanthophis and Pseudechis, 

 there is an arrangement which appears to throw light upon the 

 true homology of these parts. The osseous bars run forward and 

 converge to the mid-line, where they fuse with a small plate of 

 cartilage (?). From either side of this plate there run out two 

 well-marked tendinous bands which intersect the mylohyoid and 

 the costo-mandibular muscles. Each band runs a little forward 

 and outwards, and then turning sharply runs backwards and 

 outwards, and is lost at the posterior extremity of the mandible. 

 Thus we have a hyoid apparatus very similar to that described 

 and figured by Parker for Lacerta agilis, and also like what we 

 find in Hinulia. 



Taking this view of the hyoid apparatus, we consider that 

 the anterior intersections represent the hypohyal, and ceratohyal ; 

 the stylohyal we have seen to be attached to the quadrate. 

 The plate at the junction of the two osseous bars will therefore be 

 the basihyal. 



The second intersection will be the first branchial bar, while 

 the two ossified rods usually considered to be ceratohyals will be 

 the hypobranchial bars. 



