68 DR. H. GADOW ON THE SUCTORIAL [Feb. 20, 



]a}'er of fat. The posterior part of this muscle is fused with the 

 apex of the triangular serpi-hyoid muscle, which likewise has no 

 comiexion with the tongue. The serpi-hyoid muscle arises by two 

 slips : — first, behind the masseter, from the exoccipital bone ; and, 

 secondly, from the serpi-hyoid process. In the middle line there is 

 formed a well-developed linea tendinea. This muscle is very strongly 

 developed, and through its shape and the way of its breaking-up 

 very suggestive regarding the formation of new, secondary muscles. 

 It leaves a small empty space on each side, where there is a dead 

 point. 



A stylo-hyoid muscle is altogether absent. 



The outer riband of the m. genio-hyoideus is inserted on the 

 outer, not inner surface of the mandible. The change that the 

 insertion of this muscle has undergone, if compared with its position 

 in Nectarinia, is indicated, however, by a few muscular fibres which 

 are still attached to the neighbouring part of the ventral edge of the 

 mandible. 



The ceratoglossal muscle arises from the lateral aspect of the basi- 

 branchial ; its long tendon is inserted laterally into the anterior end 

 of the OS entoglossum and into the base of the two movable ossicles 

 forming the continuation of this bone. 



ZosTEROPS resembles Nectarinia ; but the stylo-hyoid is not 

 developed as an independent muscle. It arises from the hinder 

 angle of the mandible, and is completely united to and fused with 

 the serpi-hyoid. This appears to me to indicate that the stylo-hyoid 

 muscle is originally only the deeper layer of the serpi-hyoid. 



Certhia agrees with Zosterops ; but the combined stylo- and 

 serpi-hyoidei are very feebly developed. 



Besides these muscles, we have to consider others, which, although 

 not in direct connexion with the hyoid apparatus, act indirectly upon 

 it. The)' are tracheo-laryngeal muscles. 



In Prosthemadera we have the following : — 

 M. tracheo-laryngeits brevis et superior. It arises as a flat riband 

 from the ventral side of the upper part of the trachea, and is inserted 

 into the ventral aspect of the thyroid cartilage, a little to the side 

 of the middle line. The contraction of this muscle will bend 

 the upper larynx slightly downwards, and with it will lower the 

 tongue. 



A second pair of muscles is represented by a broad band, which 

 more or less forms the continuation of the tracheo-hyoid muscle. 

 It arises chiefly from the latero-veutral aspect of the upper third of 

 the trachea, and is attached to some cutaneous muscles on the sides 

 of the neck. In the majority of non-oscine birds it is inserted some- 

 where on the anterior border of the furcula, and is then, of course, 

 a proper m. tracheo-sternalis. 



Let us now consider how the various muscles of the upper larynx 

 and the hyoid apparatus act, and how the peculiar tongues of the 

 Tenuirostres are made use of. 



The contraction of the mylo- and serpi-hyoid muscles presses the 

 whole tongue and larynx upwards against the palatal roof of the 



