314 Cincinnati Society of Natural History. 



DE8CBIPTI0N Oi FIVE NEW SPECIES OF SILURIAN- 

 FOSSILS, AND REMARKS UPON AN 

 UNDETERMINED FORM. 



By S. A. Miller, Esq. 



Orthodesma cuneiforme, n. sp. 



Plate VIII., fig. 1, view of the right side of a cast; fig. la, view of the anterior end. 



Shell very large, equivalve, very elongate, cuneiform, ventricose, 

 and possessed of strong incurved beaks at the anterior end. The car- 

 dinal line is at an angle of about fift3'-four degrees from the basal line. 

 The beaks unite over the hmge line, at the extreme anterior part of 

 the shell, leaving a distinct lunule below. The greatest thickness 

 is at the anterior third of the shell, and from this point posteriorl3' the 

 shell is wedge-shaped. 



The length is 3 15-100 inches, thickness 1 4-10 inches, and height a 

 little greater than the thickness, but as our specimen is a cast, and some- 

 what injured on the basal line, we are unable to give the exact height. 



The species is founded upon a single specimen, having no part of 

 the shell preserved, which I collected several years ago, in the upper 

 part of the Hudson River Group, near Versailles, Indiana. It ma}- not 

 be a true Orthodesma, but its relations seem to be nearer to this genus, 

 than to any other found in rocks of this age. Muscular scars not ob- 

 served. 



Cleidophorus chicagoensis, n. sp. 



Plate VIII., fig. 2, view of the right side of a cast ; fig. '2a, dorsal view. These illustra- 

 tions are not satisfactory, and fig. 2 is specially defective in giving a view as if depressed, 

 instead of showing the true gibbous character of the fossil. 



General form of the shell, sub-elliptical, anterior extremity narrowed, 

 broader posteriori}', base regularly rounded, very ventricose in the 

 umbonal regions, and down the posterior umbonal slope. Beaks highly 

 elevated, hinge line slightl}^ arched but arcuate, in front of the 

 beaks, where the lunule is strongiv marked. The depressed line indi- 

 cating the place of the clavicle, extends from the cardinal margin, an- 

 terior to the beaks, half way to the base. The elevated ridge extend- 

 ing from the beak to the posterior basal margin, and constituting the 

 gibbous portion of the shell, fades away graduall}^ toward the anterior 

 and basal margins, and abruptly toward the hinge line. A depression 



