160 DR. R. W. SHUFELDT ON [Apr. 1, 



take on the same direction as the fibres of the temporalis, of which 

 it seems almost to be the anterior part, and passing downwards and 

 forwards, they are inserted, being somewhat tendinous, into the 

 inner aspect of the ramus of the mandible, below and at the same 

 time behind the coronary process '. 



6. Neuro-mandibularis. — Both this and the next muscle are but 

 feebly developed in our present subject, and so much alii<e are tliey, 

 both in their origins and insertions, as well as in the direction of 

 their fibres, that one might easily mistake them for one and the 

 same structure. The neuro-mandibularis is the more posterior of 

 the two, and upon either side it arises from the hinder free margin 

 of the parietal bone, from its mid-posterior point for a distance out- 

 wards of about four millimetres. It is thin and tendinous here, but 

 soon gathers itself into a small, somewhat laterally flattened, bundle 

 of fibres which pass directly downwards to the posterior tip of the 

 mandible, where they make a firm tendinous insertion. 



7. Digastric. — Is rather a smaller muscle than the neuro-mandi- 

 bularis, being related to it as we have already described in the 

 foregoing paragraph. It is the muscle of the deep layer which goes 

 to form the posterior fleshy border of the aural opening, the mylo- 

 hyoideus postei'ior being the superficial one. It arises from the 

 point of meeting of the quadrate, squamosal, and parietal bones, at 

 the postero-lateral aspect of the cranium, and passes directly down- 

 wards to make a common insertion with the neuro-mandibularis on 

 the hinder end of the lower jaw. 



Mivart does not allude to the neuro- mandibular is as occurring in 

 either Parson's Chamseleon or in the Iguana, while Sanders de- 

 scribes it as being present in Phrynosoma, as well as in Liolepis. 

 Hoffmann recognizes it in his general account of the myology of 

 Lizards, while again Mivart (Elem. Anat. p. 311) figures two digas- 

 trics for Menopoma, the posterior one of which I take to be the 

 neuro-mandibularis. 



Muscles of the Hyoidean Apparatus, 



8. Genio-liyoideus. — This is a flat muscular sheet composed of 

 fasciculi of coarse fibres, which, with the fellow of the opposite side, 

 forms a substantial fleshy underflooring to the buccal cavity. 

 Either genio-hyoid arises, carneous, from the entire anterior surface 

 of the corresponding thyro-hyal of the hyoid, and its fibres, con- 

 verging but very slightly, pass directly forwards to become inserted 

 along the inner aspect of the ramus of the mandible for the middle 

 third of its length. The deeper fibres of this muscle pass upwards 

 to become inserted into the base of the tongue. This muscle is 

 inclined to be more tendinous at its insertion than it is at its origin, 

 where in front it is separated from its fellow by quite an interval. 



9. Cerato-hyoideus. — By dividing the genio-hyoideus transversely 

 through its middle and reflecting back the cut extremities, we 

 expose the deeper set of the iiyoidean muscles. The cerato-hyoideus 



' I fail to find a " superficial temporal " in this lizard, as is described by 

 Mivart in Chamceleon parsonii (P. Z. S. 1870). 

 [14] 



