134 THE VOYAGE OF H.M.S. CHALLENGER. 



Remarks. — If this muscle does not correspond to the quadrato-sphdnoidal of Gervais 

 and Alix, I have failed to identify the latter. 



Muscles of the Hyoid Bone. 



In describing these muscles, I have made use of the terms employed by Geoffroy 

 St. Hilaire, to designate the various elements which constitute the hyoid bone of birds. 

 I have done so for the reason that whilst these names serve sufficiently the purposes of 

 accurate description, their adoption does not necessarily commit the author to any 

 particular theory regarding the morphological equivalence of the elements in question. 



The muscles arising from each hyoid cornu together form a muscular sheath, which 

 invests the whole of the cerato-hyal, as weU as the posterior half of the apo-hyal bone. 

 This sheath becomes separated anteriorly into three distinct muscles. The first of these 

 is the 



1. Cerato-glossus. 



Cerato-glosse, Cuvier, vol. iiL p. 268, No. L 

 L'ahaissmir de la langite, ISIeckel, vol. viii. p. 172, No. 1. 

 L'hyo-glosse, Gervais and Alix, p. 18. 



Attachments. — The cerato-glossus is a very delicate muscle, which, after being 

 diflFerentiated from the muscular sheath above referred to, terminates on a slender tendon 

 which courses along the lower surface of the hyoid cornu, and is inserted into the 

 anterior extremity of the glosso-hyal cartilage, close to the tip of the tongue. 



Action.— This, muscle, acting in conjunction with its fellow of the opposite side, 

 depresses the free extremity of the tongue. 



Nerve supply (?) 



2. Cerato-traiisverse muscle. 



Zungenheinhornmuskel, Tiedemann, p. 121, No. 3. 

 Cerato-hydidien, Cuvier, voL iii. p. 247, No. 4. 

 Muscle No. 4, Meckel, vol. vilL p. 177. 

 Cerato'idien transverse, Gervais and Alix, p. 19. 



Attachments. — This, the second muscle derived from the common muscular sheath 

 which envelops the cornu of the hyoid bone, separates from the common muscular mass 

 opposite the junction of the cerato- and apo-hyal elements of that bone. It passes 

 obliquely forwards and inwards, and is inserted, along with its fellow of the opposite side, 

 midway between the two halves of the lower jaw into a strong fascia which covers the 

 lower surface of the mylo-hyoid muscle. 



