30 H. B. POLLARD. 



We have therefore in these labials remnants of prernaxillary, 

 maxillary, and coronoid tentacles. To put the homologies, which I 

 maintain, into uumistakeable form, I will refer to Midler's figure of 

 Callorhynchus. I take his " ausserer Nasenfliigelknorpel e " to be the 

 remnant of the prernaxillary tentacle, his "oberer Seitenknorpel 

 des Mundes c" to be a remnant of the maxillary tentacle, his " unterer 

 Seitenknorpel des Mundes b " to be the coronoid tentacle, his " innerer 

 Nasenfliigelknorpel f" to be the nasal labial or remnant of nasal 

 tentacle. 



Then the remaining piece, the " Trager der Lippenknorpel und der 

 Nasenfliigelknorpel d " can only be the prepalatine piece, precisely as 

 Cuvier maintained. 



The labials of Selachii are then easily shown to be prernaxillary, 

 maxillary and coronoid tentacles. 1 



Further, by comparison of Holocephali and Dipnoi it is rendered 

 probable that the posterior upper labial of Ceratodus, as described by 

 Huxley, and one of the antorbital cartilages of Protopterus, as repre- 

 sented by Wiedersheim and Rose, and other authors, are homologous 

 with the prepalatine piece, and to proceed outside the limits of the fish, 

 the " Cartilago labialis superior " of the Anuran tadpole, as shown in 

 the splendid work of Gaupp, is also a prepalatine piece. In Dactylethra 

 larvae it bears a maxillo-coronoid tentacle. 



There still remain some few structures to be considered. Sagemehl 

 has described certain small cartilages in the region of the articulation 

 of the maxilla, which he terms submaxillaria, in Catostomidae, Gymnotus 

 and Perca. He homologizes them with the upper labials of Selachii, 

 giving, however, no figures, and adding that they correspond to the 

 two small upper labials described by Parker in Salmon embryos, where 

 always supposing Parker's figures to be correct, they belong rather to 

 the premaxilla. 



Then, also, there are the " Mundwinkelknorpel " refei-red to by 

 Midler and Stannius. That of Polyptems is the coronoid labial, as it is 

 attached to the coronoid process. In othei'S more definite observations 

 are needed to show whether these "Mundwinkelknorpel " are coronoid 

 or mental pieces. 



1 The lower labial of Selachii may, however, prove to he extramental, in 

 which case the coronoid would be absent as a rule. In Scymnus there is a 

 mass of soft cartilage along the upper jaw which might then represent the 

 coronoid. 



