104 paleontology of ohio. 



Beyeichia Chambersi. 



Plate 4, figs. 11, 12. 



Beyrichia Chamhersi, S. A. Miller; Cin. Quart. Jour. Sci., A^ol. I., p. 234, fig. 27; July, 

 1874.* 



Carapace minute, the extreme length not exceeding half a line, and 

 the greatest width not more than two-thirds as much as the length. 

 Form of the valves broad ovate, with one side, for a space equal to about 

 one-fourth of the width of the figure, cut away, forming the straight 

 hinge line, which is equal in length to about six-sevenths of the entire 

 length of the carapace. Greatest width of the valve a little more than 

 one-third of the length from the anterior end. Surface of the valves 

 highly convex, most prominent near the middle of the length, crossed 

 by three curving sulci, none of which reach the ventral border, the mid- 

 dle of the curve being directed toward the posterior extremit3\ The 

 middle sulcus is stronger and much deeper than the others, while the 

 posterior one is faintly marked, and situated at about the posterior third 

 of the length. The anterior sulcus is short, comparatively deep, nearly 

 semicircular, and situated within the anterior third of the length, and 

 about midway between the cardinal and basal borders. From the an- 

 terior margin of this depression, or between it and the anterior border 

 of the valve, there rises a strong, thickened, lanceolate, or scythe-shaped, 

 curved spine, which equals in length two-fifths, or sometimes one-half, 

 that of the entire valve. The anterior and posterior surfaces of the sjDine 

 are convex, the latter most strongly so, while the lateral edges are sharp, 

 and the ventral one generally deeply serrate, although a few specimens 

 have been noticed without the serrations, perhaps from wearing. The 

 margin of the valve is bordered by a thickened rim, within which there 

 is often a slightl}'- depressed channel. Surface of the crust smooth, or 

 very finely granulose. 



The si^ecies is remarkable for the strong, backward curving spine, situ- 

 ated close to the anterior border, and by this character alone can be 

 readily distinguished from any other form known from the Silurian rocks 

 of America. Several examples have been noticed where the spines have 

 been broken awaj^ just above the base, and in this condition might be 

 mistaken for a specimen of B. octdifera, to which it bears considerable 



* Some months subsequent to writing this description, the species was described 

 under the above name, loc. cit., by S. A. Miller, and as our description had not been 

 published before this time, his name will be used. 



