612 B. F. Kingsbury and H. D. Eeed. 



Beneath the facial nerve, between columella or operculum and pala- 

 toquadratCj is only loose connective tissue, denser in some forms 

 it is true,— especially Siren which possesses well developed hyo- 

 columellar and hyo-suspensorial ligaments giving a less direct sus- 

 pensorio-columellar bridge of dense connective tissue. It does not 

 seem in any form to possess relations of functional or morphological 

 importance as a ''suspensorial" connection of the ''sound-transmit- 

 ting" apparatus. 



While the presence or absence and relative development of these 

 ligaments appears to be an expression of the mechanical needs, re- 

 quirements of support in the nature of a physiological adaptation 

 and therefore secondary phylogenetic importance, their existence 

 may possibly have a deeper significance ; the ligamentum hyo-col- 

 umellare, for example, indicating a primary relationship of colum- 

 ella to the hyoid arch. 



The junction of the ceratohyal with the palatoquadrate is quite 

 constant. It is in relation to the hyo-quadrate ligament that the 

 processus hyoideus palatoquadrati is developed in so many forms 

 (see Wiedersheim "77, p. 533). 



The diagram reproduced as Fig. 21 illustrates the relations of 

 these three ligaments. 



The Hyomandihular-Symplectic Homology. It may be safely 

 stated that from the phylogenetic side the hyomandibular homology 

 of the Amphibian sound-transmitting apparatus is at present gener- 

 ally accepted, as may be seen from the statements in the works of 

 Wiedersheim and Gaupp which were cited (p. 552) as expressing the 

 more recent interpretation. In the earlier form of the theory, how- 

 ever, only a portion was given a hyoid or hyomandibular homology ; 

 Keichert, Huxley, Parker, and others regarding the operculum as 

 purely of otic origin. 



This hyomandibular homology has been reiterated despite a dearth 

 of evidence from the ontogenetic side. In the Anura, it is tnie, 

 the embryological evidence has been furnished especially by the 

 monograph of Gaupp, and it has seemed to support the partial 

 homology of the older workers, — if supporting it at all. l^o direct 

 connection has been found with the ceratohyal in development. In 



