\r/r Sprcics of Fossi/s fi-(;ni Oli'm. 21.") 



The following species arc from the limestones above the 

 "B»ne-bed," which rest on the toj> of the ftlarcellus Shale, in 

 the vicinity of Colnmbus, Ohio, and are not known to pass be- 

 low that horizon at any locality in ihat region. 



(rilbcrf^iicfi iiKs spi itifcni^ — Ti'diutlorri mis ■ytinU/ei'Hs. llall; 

 15th Ee])t. X. Y. State Cal). . p. \2S\ — (1 ilbertsocrintts {Jreiin/- 

 tocrinns) sjii/u'i/eriis, llall: De.ser. of JS'ew Species of Orinuidea, 

 from the Curbonif. Roek of the Miss. Valle}', Plate 1, Fig. '.). 



Sjiirifcra zivzac. llall. 

 Fterineafl.dheUa, Conrad's sj). 

 Grainmiisia hisulvdla, Conrad's sj). 



Aetiiiodesiiia ^ubrecta., n. sp. 



Pal. O., Vol. Ill, Plate 7, fig. 20. 



Shell of moilerate size; the body of the shell, exclusive of the wings and 

 hiuge-exteusions, ovate in outline, and slightlj' oblique to the cardinal line. 

 Hinge-line extended in the form of strong auriculations or wings on the sides 

 of the shell, the upper margin straight, or a little declining on each side of 

 the beak; anterior wing short, triangular, and divided from the body of the 

 shell by a deep and wide sub-triangular notch ; posterior side long and sub- 

 mucronate at the extremity, three to three and a half times as long as the 

 anterior side, and its area much greater, extending along the body of the 

 valve to nctU'ly half its length from the beak. Body of the left valve more than 

 moderately convex, and strongly arcuate or bent between the beak and base 

 of the shell ; so that when placed on a flat surface, the margin, especially on 

 the posterior side, would be much elevated above the plane. Beak of the 

 valve large, sub-tumid, and slightly extended above the cardinal line. Length 

 of the body of the shell, from the cardinal line to the base, about one-fifth 

 greater than across it in the opposite direction. Anterior border broadly 

 rounded, the basal margin more sharply so, with a slight angularity at its 

 junction with the nearly direct posterior border. Surface of the shell mark- 

 ed by irregular, concentric, strongly lamellose lines, resembling those of the 

 oyster. Right valve not yet observed from Ohio. 



The species is allied to A. recta — Avicula recta, Conrad, hut 

 is shorter, more ventricose on the left side, more arcuate or 

 bent, and witli less extended wings. It is not an uucoramon 

 species in the soft shales of the Hamilton group of New York, 

 where it is readily recognized from A. recta by the above-men- 

 tioned characters. The ^i. recta is most common in the arena- 



