Dr. L. Hussakqf — U. Devonian Arthrodira from Ohio. 127 



only by two small fragments, the anterior point of one and the 

 posterior end of the other ; and these, as far as one may judge from 

 such fragments, indicate a very slender type of mandible quite like 

 that of Stenognathus, and thus strengthen the view that D. Gouldi 

 belongs in the genus Stenognathus. 



The specimen in the British Museum is shown in the photograph 

 (PI. VIII, Fig. 5) and in the outline figure in the text (Fig. 6). The 

 cranium (Cran.) is shown from the inner aspect. It is of about the 

 same size as that of D. Gouldi. It is too imperfectly preserved to 

 show much of the detail except the pineal foramen. The eyes in this 

 species must have been of quite extraordinary size. 



Pig. 6. Outline of bones of Stenognathus Gouldi (Newb.), exposed on slab 

 shown in PL VIII, Fig. 5 (Brit. Mus., P. 9335). Cleveland Shale (Upper 

 Devonian) : Ohio. Explanation of letters on bones : ADL. anterior dorso- 

 lateral ; AVL. anterior ventro-lateral ; CI., CI', claviculars (imperfect); 

 Cran. cranium, inner aspect, and showing the pineal foramen ; DM. 

 dorso-median ; Mnd. mandibles, the left in inner view, the right in outer ; 

 Mx. left maxilla, outer view ; P.mx. left premaxilla, inner view ; SO. 

 suborbital ; x, x. fragmentary plates. 



The suborbital (SO.) agrees entirely with the one figured by Newberry 

 in D. Gouldi in his Paleozoic Fishes of North America, pi. ix, fig. 4. 



The clavicular (CI.), which is incomplete in the specimen, is some- 

 what different from the same element in JDinichthys, emphasizing the 

 generic distinctness of this form. 



The dorso-median (DM.) resembles the one in Newberry's specimen ; 

 but since the latter, like the one in the present specimen, lacks the 



