LAMELLIBRANCHIATA. 293 



the pallial line marked by radiating vascular striae. (These striae, by mistake 

 in the figure, are continued over the umbonal region, where they do not exist.) 

 Three specimens have the following dimensions respectively: Length 51, 

 68 and 70 ram., height 26, 35 and 37 mm. 



This species bears some resemblance in its general form to M. Tioga, but the 

 anterior end is more produced, the posterior extremity less regularly rounded, 

 and the surface markings are more rigid and less lamellose. The reference of 

 figs. 5-11, plate xl, to this species, in the Plates and Explanations, cited above, 

 arose from copying an erroneous record, without comparison ; the specimens do 

 not belong to the genus Modiomorpha. 



Formation and locality. In the Waverly sandstone, Granville, Licking county, 

 Ohio. 



GONIOPHORA, Phillips. 1848. 



GONIOPHORA PERANGULATA. 



PLATE XXXIV, FIGS. 1-6 ; AND PLATE XLII, FIGS. 1-2. 



Sanffuinolites perangulatux. Hall. Prelim. Notice Lainellibi-amhiata, 2, p. 35. 1870. 



" " S. A. MiLLKB. Cat. Ainer. Pal. Foss., p. 203. 1877. 



Oimiophorapemnffiilata,.llA.i.L. S. A. Miller. Cat. Amer. Pal. Foss., p. 1!)2. 1877. 



" •' " Pal. N. Y., vol. .5, pt. 1. Plates and Explanations : PI. 34, figs. 1-6. 1883. 



Shell of medium size or smaller, trapezoidal ; length equal to twice the height; 

 basal margin regularly curving for the greater part of its extent with an 

 undefined sinuosity about the anterior third of the length, and a slight con- 

 striction near the posterior extremity ; posterior margin obliquely truncate 

 to the cardinal line, which is nearly straight. Anterior end short, abruptly 

 rounded below, sometimes obscurely limited by an undefined depression 

 extending from the beak to the base of the shell. 



Valves convex, gibbous in the anterior portion, abruptly declining to the 

 basal and post-basal margins. 



Hinge-line nearly straight, slightly a.scending from the anterior end, 

 equalling half the length of the shell. 



Beaks anterior, small, acute, closely incurved. Umbo acutely angular; 

 umbonal ridge, with a slightly downward curve, extending to the post-basal 

 38 



