115 



its insertion. The action of the muscle is to draw the 

 lower jaw backward, and perhaps to open the mouth by 

 the short lever, whose length is the interval between its 

 insertion and the glenoid fossa. There is considerable 

 doubt whether this muscle can.be the homologue of the 

 Digastricus. 



The muscles of the tongue are very complicated, and 

 of great size. This fact is directly connected with the 

 varied movements which the tongue has, together with 

 the probable motion of a peculiar structure at its base. 

 The posterior part of the tongue is armed with rows of 

 teeth-like bodies, which also appear on the roof of the 

 mouth above. Their function may be to clear the tongue 

 of the insects which adhere to it, or in a measure to 

 bruise the food before it passes into the ossophagus. 



M. Sterno-glossus Superior. 



The two Sterno-glossi are the most abnormal of all the 

 muscles of Tachyglossa. When the neck of the animal 

 is opened from the side, there appears a round muscle of. 

 about the size of a pipe-stem, which is easily confounded 

 with the oesophagus. This round muscle is composed of 

 the Sterno-glossus Superior and Inferior united together. 

 The Sterno-glossus Superior arises on the under side of 

 the Sternum, and its fibres are continued into the tongue, 

 forming, with its fellow, the interior of that organ. Be- 

 fore it is prolonged into the tongue it is crossed by layers 

 of flat muscles, which extend over it, in front of the pos- 

 terior portion of the tongue. There is no tendinous part 

 to this muscle. Its width is uniform and about 5 mm . Its 

 length from the origin to the base of the tongue is 70 mm . 



O 



The action of the muscle is to draw back the long tongue. 



O O 



The muscular fibres, binding it down at the base of the 

 ESSEX INST. BULLETIN. ix 8 



