34 Aug. F. Focrstc 



and the typical specimens from Canada, the absence of a broad, 

 though very shahow median depression along the anterior part of 

 the pedicel valve of the Cincinnatian specimens has been seized 

 upon. In addition to this, attention is called again to the tendency 

 toward a subquadrate outline in case of the brachial valve, at least 

 posteriorly, owing to the considerable lateral extension of the hinge- 

 line. If these features do not prove comparatively constant for the 

 Cincinnatian specimens, all attempt to distinguish them under a 

 feeparate designation may prove of little value. 



The internal markings, as might have been suspected, are 

 closely similar to those of Cafa.cyga errat'ica. The hinge-plate of the 

 brachial valve consists of two stout processes separated by a sharp, 

 narrow cleft, from each side of which the crural bases extend 

 straight forward, separated by a distance of one millimeter at a 

 distance of 2 mm. from their points of atLachment. A low. flat 

 inedian elevation extends forward, becoming tripartite at a dis- 

 tance of about 4 or 5 mm. from the beak, the middle division being 

 3ong-er. more narrow, and sharper. Exterior to each of the lateral 

 divisions, an additional parallel low elevation is present. A short 

 distance anterior to the pedicel cavity of the pedicel valve, a bharp. 

 narrow median groove starts forw^ard across the muscular area. On 

 each side, posteriorly, there is a low elevation, broadening and 

 thickening along the middle of the muscular area, narrowing again 

 abruptly anteriorly, and bordered laterally at their distal extremitie.s 

 by a distinct and rather narrow depression. The thickening of the 

 shell in the region of the muscular area terminates abruptly across 

 the center of the valve. It is crossed by several radiate lines not 

 mentioned in the preceding description. 



The chief horizon for the Cincinnatian specimens of Cata::yga 

 hcadi is at the lower HehcrtcUa insculpta horizon, at the base of the 

 upper, or Blanchester division of the Waynesville bed, and in the 

 immediately overlying and underlying strata. It is found at the 

 base of the Blanchester division, immediately above HcbcrfcUa in- 

 sculpta, along the creek a mile west of Blanchester, Ohio, and also a 

 mile northeast of W'oodville, along Stony creek, abouc three miles 

 south of the Blanchester locality. It is common immediately above 

 HcbcrfcUa insculpta in Adams county, Ohio, along a road crcxssing 

 Eao-le creek, a short distance south of the mouth of Gordon run, and 

 at abouL the same horizon along a road crossing Suck run, three and 

 a half miles southwest of Bentonville, a mile east of the Suck run 



