122 NEW YORK STATE MUSEUM 



When it comes to a consideration of the dental elements in Coccosteus, 



one is somewhat surprised to find that they are compared directly with Lac- 



ertilians, much in the same way as Cope compared Macropetalichthys with 



Stegocephalians. The continuation of the above passage reads as follows : ' 



Ueber die Bezahnung der Kiefertheile habe ich noch keine voile 

 Klarheit, indess scheint mir Folgendes zu rechtfertigen. Die Bezahnungs- 

 form scheint durchaus iibereinstimmend mit der von Sphenodon. Von den 

 Zahnspitzen des Unterkiefers diirften mindestens die vordersten dem Den- 

 tale, die hinteren, mehr einwarts gelegenen vielleicht dem Spleniale zuzu- 

 rechnen sein. Die Praemaxillen scheinen entsprechend dem Vorderrand 

 des Unterkiefers mit je einer Spitze versehen gewesen zu sein. 

 Die Maxillen sind kleine schmale mehrzackige Knochenstiicke die dem 

 Innenrand des suborbitalen Astes des beilformigen Oberkieferstuckes 

 eingefiigt sind. Palatinaund Transversa habe ich noch nicht finden konnen 

 vermuthe aber ihre Existenz hinter den genannten Elementen. 



We may now give special consideration to the arrangement of dental 

 elements in Dinichthys. In the upper jaw there are always two pairs of 

 dental plates, which are clearly shown to be of dermal origin. It is denied 

 by Dean that these plates, which are commonly known as " premaxillaries " 

 and " shear teeth," can be homologized with any structures within the mouth 

 of other fishes, hence he proposes to call them by the noncommittal names 

 of " rostro-gnathals " and " orbito-gnathals " respectively, the term "gnathal" 

 being made synonymous with mandible. According to the view adopted 

 in this report, the anterior pair of upper dental plates in Dinichthys is to be 

 interpreted as vomerine, and the posterior as palato-pterygoid, thus recog- 

 nizing definite homologies between them and the like named structures — 

 which are also of dermal origin — in modern Dipnoans. The vomerine pair 

 is situated close to the median line, one on either side of the plate answering 

 In part to the dermal mesethmoid in Neoceratodus, and the tumid basal 

 expansion is received into a slight concavity on the visceral surface of the 

 preorbital. The exposed, or functional portion of the vomerine teeth is 

 cleft so as to form two vertical prongs or "beaks" of unequal length, the 



'Ueber Coccosteus und die Beurtheilung der Placodermen. Sitzungsber. Ges. 

 Naturforsch. Freunde. 1902. p. 106. 



