DESCRIPTION OF SPECIES 221 



fish plates. However, a few poorly preserved specimens of a large 

 obscure species of Naiadites were found with large numbers of Lingula 

 carbonaria on the Anthony coal horizon. Often N. elongata is so abun- 

 dant that freshly broken surfaces of shale present a mass of crushed 

 and macerated individuals. 



Horizon and locality. Sharon horizon : Scioto County, Harry Odle 

 mine, Locality 4, r; John Alexander mine, Locality 3, c. Quakertown 

 or No. 2 coal horizon: Muskingum County, Grace mine, Twin-Ada 

 mine, and Wilson mine, Localities 11, 10, 9, r. Bear Run horizon: 

 abundant in Scioto, Jackson, and Vinton counties in all localities from 

 which collections were made, Localities 13, 14, 15, 16, 17, 18, aa. 

 Boggs member: Scioto County, Bloom Township, Locality 23, a. 



Naiadites ohioense n. sp. 

 PI. XII, figs. 10-13 



Description. Shell small, obliquely elongate, gibbous, the greatest 

 thickness being a little anterior to the middle, right valve a little more 

 compressed than the left, shell gaping along ventral and posterior 

 margins; hinge line almost or entirely as long as the greatest length of 

 the shell; beaks minute, anterior but not quite terminal, incurved, 

 slightly elevated above the hinge line; anterior lobe small, prominent, 

 gibbous, projecting a little beyond the beak, rounding into the ventral 

 or inferior margin; ventral margin concave or sinuous in middle, bluntly 

 rounded posteriorly; posterior portion forming the greatest height of 

 the shell, margin straight or very slightly rounded, meeting the hinge 

 line at an angle which is either a little greater than or equal to a right 

 angle; a prominent, gibbous umbonal ridge extending obliquely back- 

 ward from the beak to the posterior-inferior angle, broadening poster- 

 iorly, but preserving its distinctive character throughout its extent; a 

 deep, oblique sinus anterior to the ridge, separating the anterior lobe 

 from the remainder of the shell; region below hinge line depressed. 

 Surface marked by fine, regular, concentric lines of growth. 



Dimensions. A cotype measures: Maximum length 12 mm., 

 maximum height near posterior margin 8 mm., length of hinge line 

 9.5 mm., convexity 6.5 mm. 



Remarks. This species of Naiadites has been found at one locality 

 in Scioto County where it is not only extremely abundant, but speci- 

 mens are often in a remarkable state of preservation, a condition very 

 unusual for representatives of this genus; the general occurrence of 

 Naiadites in Potts ville rocks of Ohio is crushed, distorted, or macerated. 

 The species under discussion occurs in nodules of iron ore and is asso- 

 ciated with N. elongata, but no other fossils are present. N. elongata 

 differs in having a shorter hinge line which is equal to less than one- 



