306 PALEONTOLOGY OP OHIO. 



anterior end; umbonal slopes very convex, or forming a prominent 

 rounded ridge from the beaks obliquely backward and downward to the 

 posterior basal margin ; flanks more or less flattened or contracted along 

 the middle near the basal margin, and thence obliquely forward and up- 

 ward to the beaks. Surface showing only moderately distinct lines of 

 growth. ' 



Length of a large, mature specimen, 1.07 inch ; height, 0.33 inch; con- 

 vexity, about 0.30 inch. 



This species will be at once distinguished from P. elegans, the type of 

 the genus, by its much greater convexity, more rhombic outline (caused 

 by greatly more oblique outline of its posterior margin), and particu- 

 larly by its more shallow and more obtuse anterior notch, and decidedly 

 more prominent umbonal slopes. 



locality and position : Eushville, Ohio, in the Waverly group of the Lower Carbonif- 

 erous series. 



Genus SAISTGDINOLITES, McCoy, 1844. 

 (Synop. Carb. Foss. Ireland, 47.) 



Sangdinolites ? OBLiQuus, Meek. 



Plate 16, figs. 2a, 6. 



Sangmnolitesf obliquits, Meek (1871), Proceed. Acad. Nat. Sci., Philad., XXLII, 13. 



Shell so depressed and elongated as to be nearly three times as long as 

 high, rather distinctly convex, particularly along the posterior umbonal 

 slopes, which are more or less angular from the beaks nearly to the pos- 

 terior basal extremity; pallial margin very nearly straight along most 

 of its length ; anterior end extremely short, and a little sinuous on the 

 upper side just in front of the beaks, the sinuosity being caused by a 

 very small, deep lunule, at the lower end of which the margin is a little 

 projecting and angular or sub-angular in outline, and from this little 

 projection it curves obliquely backward into the base ; cardinal margin 

 extending back about three-fourths the length of the valves, and in- 

 flected so as to form a well defined lanceolate escutcheon along its entire 

 length ; posterior side narrowed with a long slope above from the end of 

 the hinge to the extremity, which is a little gaping and very narrowly 

 rounded or almost angular below ; beaks strongly depressed, very oblique, 

 compressed below the ridges, very nearly terminal, and with the imme- 

 diate points incurved over the little lunule. Surface showing only lines 



