202 



F. II. KDGEWOKTH. 



shows that its primitive condition is that of a transvei'se 

 sheet passing- from one ramus of the lower jaw to the other. 

 This exists only in Salmo. In Necterus, Triton, Ceratotlus, 

 Scyllium, Acanthias, Polypterus, Lepidosteus, and Amia 

 it extends backwards, underlying the fore part of the inter- 



Text-fig. 29. 



l^kax.l!^ 



L'vCexku<vJ 



LoL .4 



s<^.R*^ouL 



hyoideus, and in Amia and Triton it divides into anterior 

 and posterior portions. In Aiiuran larvas it divides into 

 submentalis, mandibulo-labialis and submaxillaris, of which 

 the first has a special relationship to the inferior labial 

 cartilag'es. In Sauropsida it forms a continuous sheet with 

 the interhyoideus and C^vd. In Lepus it is overlapped by 

 the forward-growing interhyoideus. 



