36 THE SALAMANDER 



vestiges may persist as little cartilaginous knobs between the right 

 and left portions of the M. genio-hyoideus. 



The chief abnormality met with in the visceral skeleton is the 

 occurrence of a rudiment of a hypo-branchial^ element in the third 

 branchial (fifth visceral) arch. Four instances of such a condition 

 occurring in larvae have been reported, namely, one case of a rudi- 

 ment occurring on the left side (Kallius, 1901), two instances of a 

 rudiment of the right side (Driiner, 1901), while Helena Tarapini 

 (1909) finds in a 30 mm. larva of Salamandra atra a pair of small 

 cartilages which she regards as rudimentary third hypo-branchials. 

 During the present investigation one case has been found in which 

 cartilages apparently representing these elements occurred in the 

 adult. This has been fully described elsewhere (Francis, 1931). 

 Druner also reports cases where very small vestiges of the cerato- 

 branchials III and IV have been found in the adult, and, as mentioned 

 above, small traces of the uro-branchial shaft have occasionally been 

 noticed. 



The visceral skeleton of Salamandra, both larval and adult, has 

 received a considerable amount of attention from time to time, and 

 its several parts have been given names indicative of widely varying 

 interpretations of their homology (a list of the more important 

 synonyms is appended below). Rusconi (1854) was one of the first 

 to undertake a detailed investigation of this region in the larva as 

 well as in the adult, and his classic account of the metamorphosis of 

 both skeleton and muscles remained without any substantial addi- 

 tion until 1 90 1, when Druner, applying more modern methods, 

 reinvestigated the whole problem. Rusconi was of the opinion that 

 both pairs of radials were of secondary origin, while Walter (1887) 

 considered that they represented two pairs of hypo-hyals. Druner, 

 however, showed that the anterior pair only belong to the hyoid arch 

 while the posterior pair are new structures. Wilder, Druner, and 

 others also include the laryngeal cartilages in the visceral skeleton, 

 but Edgeworth (1920) has shown this to be erroneous (see also under 

 'Larynx', p. 272). 



Synonyms of the Visceral Skeleton. 

 Cerato-hyal = Stylo-hyal, Duges (1834). 

 Both branchial arches together = Corne thyroidienne, Duges. 

 Hypo-branchials = Kerato-branchials, Wiedersheim. 

 Cerato-branchials = Epi-branchials, Wiedersheim. 



^ It should be noted that only the cerato-branchial element is normally present in_ 

 the larval Salamander. 



