BUFFALO SOCIETY OF NATURAL SCIENCES 77 



careful cast of each half was prepared, showing the elements in relief. 

 The drawing is made from the cast of the better half of the specimen. 



Both mandibles (Mnd), are preserved; the left is shown in outer 

 view and the right in inner. Both show well the denticles along the 

 functional margin, and the right shows also the row of symphyseal 

 denticles. These are broken away and represented only by their 

 bases. 



Both antero-superognathals (ASG) are preserved, although the draw- 

 ing shows only that of the right side, in outer view. This is one of 

 the most interesting antero-superognathals known, showing the 

 structure of this element in the genus Stenognathus better than any 

 other specimen. In the specimen of Stenognathus gouldi in the British 

 Museimi, figured by Hussakof in 191 1,^^ an antero-superognathal is 

 preserved, which is somewhat similar to the present one in size and 

 form; but it is not well enough preserved to show all its characters. 

 The present specimen is therefore of great value, as showing for the 

 first time the complete element in this genus. Its form and peculiar- 

 ities are described above. 



Only the left postero-superognathal (PSG) is present, shown in 

 inner view. It is not very well preserved. When collected it had a 

 row of denticles along its cutting margin. 



Both suborbitals (SO) are present, shown in outer view. They 

 have long, slender processes, and the blades proper are very thin and 

 somewhat shorter posteriorly than in Dinichthys. The lateral canals 

 are clearly shown. 



Below the pair of mandibles is seen a fragmentary plate (LAT) 

 probably a portion of one of the laterals. 



This is the fifth species of Stenognathus to be described, and it 

 is easily distinguishable from the others. From S. gouldi of the Cleve- 

 and shale, and from S. insignis of the Conodont bed (see p. 73), it is 

 distinguished at once by the presence of denticles along the cutting 

 margin of the mandible, in these two species the cutting margin 

 being a continuous beveled edge. From 5. dolichocephalus, which 

 is from the same horizon and locahty, it differs by its much larger size 

 and by differences in the form of the various plates. From 5. denticu- 

 latus of the Conodont bed (see p. 71) it is distinguished by its larger 

 size and by the different form of the postero-superognathal. 



^Hussakof, L.: Upper Devonian Arthrodira from Ohio in the British Museum (Nat. Hist.) 

 Geol. Mag., [$\, viii, 123-128, pi. viii, and text-fig. 6, 1911. 



