570 PAL-fflONTOLOGICAL REPORT OF GEOLOGICAL SURVEY. 



CARDINIA? FRAGILIS. Cox. 

 (PI. VIII, fig. 9; left valve natural size.) 



Shell very thin ; transversely ovate; beak scarcely elevated; an- 

 terior slope slightly hollowed; anterior extremity short, rounded be- 

 low; base and posterior side obtusely rounded; hinge line straight, 

 slightly truncated behind the beak ; surface covered with broad con- 

 centric furrows; height .-jVo inch; width l.-jVk inches. 



It is difficult, from the poorly preserved specimens now collected, 

 to determine the genus with certainty ; but believing it to be a char- 

 acteristic shell, have placed it conditionally amongst the cardinia. 

 When well preserved the valves may be found ornamented with fine 

 concentric striae. 



Position and locality. Abundant in the black shale, which some- 

 times forms the roof of No. 11 coal, at Airdrie, Mublenburg county, 

 Kentucky. 



MACROCHEILUS GRACILIS. Cox. 



(PI. VIII, fig. 11, enlarged; fig. 11 a, natural size.) 



Small; conical; about six volutions; convex; suture small; last 

 whorl half the length of entire shell ; columella lip elongated; slight- 

 ly refected; mouth subovate; length .-j^inch; width .-jJ^inchj 

 spiral angle 56°. 



It differs from M. acutus, Sow.-, by the more rapid increase of the 

 whorls, prolougation of the columella lip, and less rotundity of the 

 mouth. Though the specimen under description is most likely a 

 young shell, it cannot be confounded in any stage of developement 

 with its cogenitors. 



Position and locality, Common in the shale over No. 11 coal, Bon- 

 harbor, Daviess county, Kentucky. 



ORTHIS RESTJPINOIDES. Cox. 

 {PI. IX, fig. 1, end view, natural size; fig. 1 a, entering valve; fig. 1 b, profile.) 



Hinge line straight; less than the width of the shell ; cardinal area 

 well marked, gradually sloping back on the receiving valve; large 

 angular foramen ; both valves covered with fine thread-like strise, radi- 

 ating from the beaks to the circumference, numbering on the disk thir- 

 teen in .-^ of an inch, crossed by fimbriating lines marking stages of 

 growth; obsolete on the umbo; well marked and more numerous from the 

 base for one third the length; receiving valve moder<#Jy convex ; 



