BUFFALO SOCIETY OF NATURAL SCIENCES 75 



Stenognathus mixeri, n. sp. 



(Text-fig. 25) 



E 2030 Type. — A slab of shale 29 by 46 cm., in counterpart, con- 

 taining both mandibles, an antero- and a postero-super- 

 ognathal, both suborbitals, portion of a lateral plate, 

 sclerotic segments, and several incomplete cranial and 

 ventral plates. 



Formation and Locality. Rhinestreet shale (Portage); shore of 

 Lake Erie, near Sturgeon Point, Erie County, New York. Collected 

 by F. K. Mixer and W. L. Bryant. 



Mandible 17.5 cm. in length, long and slender, the functional por- 

 tion contained i^ times in the blade portion; greatest depth of func- 

 tional portion 3I times in its length. Functional margin with den- 

 ticles except at its anterior fourth, which is smooth and beveled; 

 denticles about 1 2 in number, gradually increasing in height backward; 

 largest denticle 3 mm. high. Anterior extremity of mandible rises 

 into a low beak. Symphysis with a vertical row of 7 denticles. 

 Antero-superognathal triangular in outline, with a pointed beak and 

 a small, secondary cusp; upper or process portion of element flattened, 

 thin and not developed into an elongated thickened process as in 

 Dinichthys; outer lateral margin of element with 4 or 5 low denticles. 

 Postero-superognathal, elongated, and when found, had a row of 

 denticles along its functional margin. (This element is shown in 

 inner view and is not well preserved.) Plates of cranial shield appar- 

 ently thin. Suborbital of the form characteristic of this genus, with 

 long slender anterior process and relatively short, somewhat tri- 

 angular blade portion. Orbit very large. 



We take pleasure in naming this species for Mr. F. K. Mixer of 

 Buffalo, long an active member of the Buffalo Society and at one time 

 curator of its museum, to whom students of Arthrodira are in- 

 debted for his discovery of numerous localities of fish-bearing rocks 

 in the vicinity of Buffalo. Mr. Mixer and Mr. Bryant were 

 together on a collecting trip at Sturgeon Point, N. Y., when the 

 present specimen was discovered. 



Remarks. — This remarkable specimen belongs in the genus Steno- . 

 gnathus, a genus distinguished especially by its long, slender mandibles, 

 sub-triangular antero-superognathals, and elongated upper shear 

 teeth. The suboribtals are also characteristic, the orbits being large, 



