Remarks. This species of Naiadites has been found at one local- 

 ity in Scioto County where it is not only extremely abundant, but the 

 specimens are often in a remarkable state of preservation, a condi- 

 tion very unusual for the representatives of the genus. The general 

 condition of occurrence of Naiadites in the Pottsville rocks of Ohio 

 is crushed, distorted, or macerated. The species under discussion 

 occurs in nodules of iron ore and is associated 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-half the length of the shell; 

 also in its rounded posterior margins and its less prominent umbonal 

 ridge. N.ohionese, however, is very variable and differences exist 

 in the size and prominences of the anterior lobe, the length of the 

 hinge line, and the outline of the posterior portion. Whether these 

 points of difference are due to slight distortion or natural variation 

 among individuals, or whether more than one species is really present, 

 is a matter of question. But on account of the variable nature of 

 the genus itself, such differences are to be expected and are therefore 

 particularly difficult to evaluate. After a careful study of the material 

 at hand, it seems best to the writer to group under one species these 

 forms with the long hinge line as there seems no tangible basis for 

 further subdivision. 



Horizon and locality. Sharon ore: occurs in nodules of iron ore 

 in the John Alexander mine, Scioto County (Locality 3), aa. 



Naiadites sp. 



Several crushed, poorly preserved specimens of a very large 

 species of Naiadites were found associated with large numbers of 

 Lingula carbonaria in the black shales of the Anthony coal horizon. 

 They are, however, too poor for identification. 



Horizon and locality. Anthony coal horizon: Wm. E. Dee mine, 

 Scioto County (Locality 7), r. 



Genus Schizodus King 

 Schizodus amplus Meek and Worthen 



1870 Schizodus amplus. Meek and Worthen, Proc. Acad. Nat. Sci. Phil., p. 41. 



Coal Measures: Seaville, Fulton County, Illinois. 

 1873 Schizodus amplus. Meek and Worthen, Geol. Surv. 111., Vol. 5, p. 579, PI. 27, 



Fig. 6. 



Coal Measures: Seaville, Fulton County, Illinois. 



Description. An excellent cast of the left valve of Schizodus 

 amplus is among the collections of Boggs fossils at hand. The species 

 is characterized by its large size, quadrangular form, anteriorly placed 

 beak, and long, straight cardinal margin posterior to the beak. In 

 the specimen studied the pallial line, the large adductor scar, and the 

 anterior pedal muscular impression are distinctly marked. Other 

 less perfect specimens were obtained from the Lower Mercer limestone. 



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