56 CATALOG or FOSSIL FISHES IN THE MUSEUM 



Remarks. — This small mandible constitutes a well-marked species, 

 easily distinguished by the two widely-separated beaks, and the shal- 

 lowness of the part of the mandible between them. It differs from 

 all other dinichthyid mandibles by the fact that the cutting mar- 

 gin is longer than the blade, or inserted, portion (measured from its 

 upper junction with the functional part). The mandible as a whole 

 is also rather more slender than is usual mDinichthys; but the presence 

 of two beaks, precludes its being placed in Stenognathus. 



The specimen may perhaps belong in the same species with the 

 remarkable slender antero-superognathal described on a previous 

 page under the name Dinichthys insolitus. But there is no proof of 

 such association, and for the present it is wiser to consider this man- 

 dible a distinct species. 



Dinichthys sp. (Ventral armor) 



(Text-figs. 1 6, 17) 



E 2032 The complete ventral armor of a medium-sized species of 

 Dinichthys, on a slab of shale. The specimen is badly 

 weathered, and much of the actual bone is lost; but the 

 outli;nes of the plates can be made out, and at the pos- 

 terior end, where the tip of the postero-ventrolaterals is 

 missing, it can be supplied by continuing the outline of 

 the portion of these plates preserved. The antero- 

 ventromedian was obviously a separate plate and not 

 fused with the postero-ventromedian into a single piece. 

 To the right of the antero-ventrolaterals is a small plate, 

 shaped somewhat like an upper tooth; it is, however, a 

 thin plate and shows a centre of ossification. The frag- 

 ment seen above the right antero- ventrolateral is a por- 

 tion of an unidentified plate. 

 Total length of plastron 31 cm.; greatest width, 17. 

 Portage; Sturgeon Pt., on shore of Lake Erie. Col- 

 lected by Mr. F. K. Mixer. 



This is a very important specimen, being one of the two thus far 

 known which show the entire ventral armor of Dinichthys in natural 

 association. The other specimen is that of a small dinichthyid 

 described in 1910 by Burnett Smith.^- In this the plates were repre- 



22 Smith, Burnett: Notes on some little-known fishes from the New York Devonian. Proc. 

 Acad. Nat. Set., Philadelphia, Ixii, 656-663. 



