FOSSILS OF THE SILURIAN AND DEVONIAN EOCKS. 213 



Paracyclas ohioensis, MEEK. 



Plate V., figure 20. 



Lucina ohioensis, Meek. Proc. Acad. Nat. Sci. Phil., p. 6 1871. 



Compare Posidonia lirata, Conrad. 1838, see fig. 12, pi. 2, 13th Rep. on St. Cab. of N. Y. 

 Lucina (Paracyclas) ohioensis, Meek. Pal. of Ohio, Vol. 1, p. 199 1873. 



Shell of less than medium size ; compressed or only slightly convex, and 

 more or less nearly circular, though in some specimens greatly deviating from 

 that form, as is shown in the specimen illustrated on plate 5, figure 20 ; beaks 

 small and appressed, and very little elevated above the dorsal margin; they 

 are situated about in the center of the dorsal border. The anterior margin is 

 rather abruptly compressed above, just in front of the beaks ; hinge- margin 

 short and rounding into the posterior dorsal outline ; posterior dorsal slopes 

 of each valve marked by a strongly oblique sulcus, extending from the back 

 part of the beaks to the upper portion of the posterior margin, to which it 

 imparts a slightly sinuous outline at its termination. 



Surface ornamented with small, more or less regular, concentric undmations, 

 which are most strongly defined on the umbones. The average size of shells 

 belonging to this species is represented in the specimen illustrated on plate 5, 

 figure 20. 



This species is closely allied to Par. lirata, with which it is considered iden- 

 tical by some palaeontologists ; but its peculiar posterior dorsal sulcus is such 

 a prominent feature, that it may be regarded of sufficient importance and 

 value to base upon it a separate species. 



Formation and Locality. It occurs, together with its associates and congeners, the Par. elliptica } 

 lirata, elongata and octerlonii,5n the upper strata of the Devonian formation, in Jefferson county, Ky., and 

 in Clark county, lud. It is, however, very rare in our rocks, where, so far, only a few specimens have 

 been found. 



Genus Goniophora. Phmi ps . 



Goniophora, Phillips 1848. 



Etymology : gonia, an angle; phoros, bearing. 



Shell equivalve, very inequilateral, rhomboidal or trapezoidal in outline; 

 obliquely truncate behind and rounded in front. Cardinal line usually straight 

 and not oblique. Beaks small, closely incurved, situated within or about the 

 anterior third of the shell. Umbo prominent. Umbonal slope continued as a 

 strong angular ridge to the post-inferior margin. The valves are crossed 

 obliquely, sometimes vertically, by a broad, undefined sinus, extending from 

 anterior of the beaks to the basal margin, which is usually slightly constricted 

 at this point. 



