DESCRIPTION OF SPECIES 175 



the Sand Block ore. The . convexity is moderate, and the beak is 

 situated about two-fifths the length of the valve from the posterior 

 margin. Small portions of the external shell which remain show a 

 surface sculpture of extremely fine concentric lines. 



Horizon and locality. Sand Block ore: Jackson County, Locality 

 57, r. 



Genus Crania Retzius 



Crania modesta White and St. John 



1868 Crania modesta. White and St. John, Trans. Chicago Acad. Sci., Vol. 1, p. 118. 



Upper Coal Measures: Fremont County, Iowa. 

 1882 Crania carbonaria. Whitfield, Ann. N. Y. Acad. Sci., Vol. 2, p. 229. 



Coal Measures : Carbon Hill, Hocking County, Ohio. 



Remarks. A species of Crania is common in the middle and upper 

 Pottsville of this State which probably represents the same form as 

 that described 'by White and St. John, although judging from the 

 description, the latter was free while the Ohio form is always found 

 attached to other shells by the pedicle valve. It is likewise identical 

 with Whitfield's species, C. carbonaria, described from Carbon Hill, 

 Hocking County, a form which is always found attached to foreign 

 objects. 



Horizon and locality. Lower Mercer limestone: Perry County, 

 Locality 35, c; Muskingum County, Locality 36, c; Licking County, 

 Flint Ridge, Locality 48, r. Upper Mercer limestone: Perry County, 

 Locality 63, r; Coshocton County, Locality 72, c. McArthur limestone: 

 Vinton County, Locality 84, c. 



Genus Rhipidomella Oehlert 



Rhipidomella pecosi (Marcou) 

 PI. VII, fig. 13 



1859 Orthis pecosi. Marcou, Geol. N. Am., p. 48, PI. 6, Fig. 14. 

 Mountain limestone: Pecos Village, New Mexico. 



Remarks. This small shell with its almost circular form and its 

 fine radiating lines is rather rare in rocks of Pottsville age in this State, 

 but it is most frequent in occurrence in the Lower Mercer limestone. 

 In the collections of Lowellville limestone it is represented only by a 

 single ventral valve which measures: length 6.5 mm., width 7.7 mm., 

 convexity 2 mm. 



Horizon and locality. Lowellville member: Muskingum County, 

 Locality 19, r. Low^r Mercer limestone: Scioto County, Locality 31, 



