PRAOOD4 



i|Ui>la ) 



Ki I:M-IIII i VTA. n 



inn ; hurl U; thlrkm-^0 ..> lulu 



Wit: -niii. 



Valve- i|iiadrate--iil'elliptical in outline, strongly convex. \\itli the dorsal angles 



ol'ttiM', the end- rounded, and the dor.-al and ventral margin- nearly parallel. I'.ody 



of valve rather uniformly convex, \\ith the anterior end a trille more obliquely 



rounded than the po-terior. Sulcu- -itnated a little liehiud the center, deep, narrow. 



.light dor-al border and terminating abruptly at a point le than 



one- third of the hight of the valve lie neat li it. On each side of the -nlcn- the -urface 

 rises into a low eminence. one. -uppo-ed to l.e the posterior, a little higher than the 

 other. Central portion of >urface exhibiting numerous, rather irregularly distrihu- 

 ted pn-tiile-. I'.'irder not defined by an impr.- - I -nture line, flattened except at it- 



me outer edge \\here it liend- -uddenly inward. Its surface presents more or 

 less oli-rure radial eries of minute granule-.. im.~t distinct on the ventral iiortion 

 whore the horder is al.o the widi- 



A- itated under the generic tion. ti ne of a number of species 



l-elon^iiiL' to an unde-crihed |?enus. Of these form- /. P trit<ini<ii-<iinat<i Miller, 

 from the nppermo.-t l>ed- of the ( 'incinnati formation, and /-.'. '' i<h, >// 1'lrich, from 

 the Hirdseye limestone of Kentucky, are prohaUy the nearest. The first is less 

 convex, ha- a diilerent sule> and a wider lntnler, marked with fine radiating lines 

 in-tead of nw> of Crannies. The latter agrees very well in most respects but may 



i-tingui>hed at once \>\ the alienee of any well defined stilcu-. 



.'i.'y I !! r ilnr.1 of II . h> ;i..|-,nii.t l-'li. SI. Paul, MlnnMoU. 







Kri:v< IIII.IN i:n v, u 



r I \ I I 



h I s inin : liik'tit 1 I i! xur.HiiO-4 t- 



hi 7 linn.: hl^tu I ' - mm. 



Valve- -iiKelliptical or -omewhat ipiadrate. e.|in'lateral. greatly c pressed, 



l.i'i _'.<> nun. in length. I>or-al margin -tiaight or slightly convex, a little shorter 

 than the valve; dor-al angle- not very -harp: ventral margin >emielliptical. curving 

 n.-atly into the rounded end-. Mody of valve tlattoned. lnit ri-ing at two points near 

 the hinj?e, each situated aliout midway letween the dorsal angles and the center, 

 into two, more or less prominent, large subequal rounded tulx-rde-. These are 

 connected l>yathin ridge, the two bulbs and connecting liar resembling the old "bar 

 shot." Surface broaoly excavated centrally, and marked with obscure pit-. Marginal 



