FOSSIL FISHES. 9 



i. e., whether they are the homologues of the anterior, vomei'ine teeth of Lep- 

 idosiren, or whether they represent the anterior folds of the great " palato- 

 pterygoid" dental plates, separated from their maxilla-like wings,— though 

 one of interest, does not materially affect the greater question of the gen- 

 eral relationship of Dinichthys to Lepidosiren. The minor question 

 will doubtless be settled in due time by the discovery of some specimen 

 in an unusual state of preservation. The broader and more important 

 one, it seems to me, maybe decided from the material now before us. 



Whatever may be said in regard to the dentition of the upper jaw, the 

 peculiar mandibles of Lejpidosiren and Dinichthys are so alike in every 

 essential particular that they would seem to afford evidence of relation- 

 ship, even if all other proof was wanting. On the whole, the correspond- 

 ence between the dentition of Dinichthys and Lepidosiren is so remark- 

 ably close that it seems to afford good ground for believing that we have 

 in the latter the dwarfed and diminished representative of the great group 

 of fishes which, in the Devonian age, populated and dominated the waters 

 of the globe ; and that the peculiar dentition of Lepidosiren is a remnant 

 of an antique fashion once much in vogue but now ol)solete, except as 

 preserved in this little living Dipnoan. The proof of relationship 

 between Dinichthys and Lepidosiren seems to be at least as satisfactory 

 as that of Ceratodus Forsteri of Australia with Ceratodus of the Trias, 

 Ctenodus of the Carboniferous, and Dipterus of the Devonian ; and if the 

 view here presented should be accepted, the facts cited will, perhaps, not 

 be regarded as less important and suggestive than those connected with 

 the discovery of a living species of Ceratodus. 



The relations of Dinichthys to other fossil fishes, as revealed by the 

 series of specimens found during the past year, are no less interesting than 

 those which this great fish bears to the living Lepidosiren. TJie most 

 striking specimens obtained by Mr. Terrell are the bones composing the 

 ventro-pectoral and dorsal shields; both of which are almost entirely 

 complete. These are so perfectly represented in the figures now pub- 

 lished (Charts Y. and VI.— natural size, from photographs) that no 

 detailed description of them will be requu-ed. The large view given of 

 the pectoral and ventral bones represents their inner surfaces, and they are 

 somewhat separated in order that their outlines may be more clearly 

 shown. In the subjoined wood-cut, however, they are represented (one- 

 tenth natural size, linear) in their natural positions, as seen from the outside. 

 By comparing this plastron — if we may so call it — of Dinichthys, with 

 that of Ooccosteus, which is also given below in outline, it will be seen that 

 they correspond in all essential particulars ; so much so that the bones 

 which compose them might be taken to be the homologous parts in different 

 species of the same genus. It is true that the ventral shield of Ooccosteus, 



