The oral cirri of Siluroids and the origin of the head in Vertebrates. 407 



Seitenkiiorpel des Mundes &" to be the coronoid tentacle, his "innerer 

 Nasenfiiigelknorpel /"' to be the nasal labial or remnant of nasal tentacle. 



Then the remaining piece, the "Träger der Lippenknorpel und 

 der Nasenflügelknorpel d'' can only be the prepalatine piece, precisely 

 as CuviKR maintained. 



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

 maxillary and coronoid tentacles ')■ 



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 Proiopterus , as 

 represented by Wiedersheim and Rose, and other authors, are homo- 

 logous 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 Dncti/Iethra larvae it bears a maxillo-coronoid tentacle. 



There still remain some few structures to be considered. Sage- 

 mehl has described certain small cartilages in the region of the arti- 

 culation 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 corre- 

 spond 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" referred to by 

 MCller and Stannius. That of Polypterus is the coronoid labial, 

 as it is attached to the coronoid process. In others more definite 

 observations are needed to show whether these "Mundwinkelknorpel" 

 are coronoid or mental pieces. 



Certain muscles in Teleostei, considered by Vetter superficial 

 portions of the adductor mandibulae, proceed, not to the lower jaw 

 but, to the maxilla and neighbouring parts. The Adductor tentaculi 

 of Amiurus, described by Mc Murrich, is one of these. In CoUtidae 

 (Misgurnus) they are very large, lal)ial muscles also being present in 

 correspondence with the presence of the tentacles. Vetter states that 

 they are innervated by a special motor branch of the Trigeminus. 

 They correspond to the Retractores tentaculorum of Myxinoids, and 

 are a further proof of the correctness of the views here maintained. 



1) The lower labial of Selachii may however prove to be extra- 

 mental, in which case the coronoid would be absent as a rule. In 

 Scymnus thoro is a mass of soft cartilage along the upper jaw which 

 might then represent the coronoid. 



