HYOBRANCHIAL APPARATUS OF SPELERPES 537 



broad flattened proximal end quite free in the floor of the mouth 

 and projecting sUghtly into the double fold of mucous membrane 

 dorsal to the tongue stalk (figs. 23 and 24). Posteriorly it 

 becomes narrowed and more rounded, dorsal to the cerato- 

 branchials, till a little posterior to the articulation of the mandible 

 it hooks around, laterally and then anteriorly and has its distal 

 end firmly attached to the quadrate bone. 



Of the cartilages of the central portion, the first basibranchial 

 is the pivot, as I have already stated. This median cartilage lies 

 in the tongue stalk and is somewhat curved anterodorsally, with 

 its anterior end in the substance of the tongue (fig. 2) . Its ventral 

 surface is flat and, for the anterior two-thirds, is broadened by 

 lateral cartilaginous shelves, formed at metamorphosis. On the 



Fig. 2 Median sagittal section of tongue and tongue-stalk of adult. 



dorsal surface these shelves help to form rather deep lateral 

 grooves in which the abdominohyoideus muscles lie. The pos- 

 terior third is more cylindrical and tapers sharply at the tip like 

 the basibranchial of the larva. 



A pair of 'little horns,' such as are quite universally present 

 among adult Salamandrids, occurs at the anterior end of the 

 basibranchial. These coruna articulate with the basibranchial 

 anteriorly and extend laterodorsally into the disk of the tongue. 

 Between the horns and dorsal to the basibranchial, is a tiny 

 y-shaped lingual cartilage (figs. 18 and 22) of which I find no 

 mention in any of the description of the visceral skeleton in 

 Plethodontidae. From its position, however, and from its 

 function as the origin of the hyoglossal muscle, it is undoubtedly 

 the morphological equivalent of the 'Sehnen-platte' which Oppel 



