WAVERLY GROUP SPECIES. 279 



This species is remarkable for its nearly marginal apex, which is, in- 

 deed, placed almost exactly over the posterior margin, though raised 

 about one-tenth of an inch above it. I am not sure whether it is a true 

 Discina or not, as I have seen no specimens of the under valve. I sus- 

 pect that it will prove to be an Orbiculoidea, as several of the species de- 

 scribed under the name Discina, from this horizon, seem to possess the 

 peculiarities of the foramen in the under valve distinguishing the 

 former group. This is certainly the case with D. Saffordi of Winchell, 

 and the form I have identified with D. Newberryi. 



Locality and position : Newark, Ohio. Waverly group of Lower Carboniferous series. 



Genus STROPHOMENA, Eafmepque, 1827. 



Sub-genus HEMIPRONITES, Pander, 1830.* 



(Beitr. zur Geog. de Russ., 74.) 



Hemipronites CRENI8TRIA, Phillips ? (sp.). 



Plate 10, figs. 5a, 6, c, d. 



Spirifer crenistria, Phillips (1836) ; Geol. Yorkshire, Vol. II., pi. 9, fig. 6. 



Spirifer senilis, Phillips; lb., fig. 5. 



Leptima anomala, J. de 0. Sowerby (1840) ; Min. Conch., tab. 615, fig. 16. 



Orthis umbraculum, var. Portlock (1843) ; Geol. Londonderry, Tyrone, etc., pi. 37, fig. 5 : 



DeKoninck (1843) ; Anim. Foss. Terr. Carb Belg., p. 222, pi. 13, figs. 4-7. 

 Orthis Sechei, McCoy (1844) ; Synop. Carb. Foss. Ireland, pi. 22, fig. 3. 

 Orthis comala and 0. caduca, McCoy (1844) ; lb., figs. 5 and 6. 

 f Orthotetes radians, Fischer (1850) ; Bull. Soc, XXIII., pi 10. 

 Leptxna crenistria and L. senilis, McCoy (1855) ; Brit. Pal. Foss., pp. 450 and 452. 

 Stzeptorhynchus crenistria, Davidson (1860) ; Monogr. Scottish Carb. Brach., p. 32, pi. 1, 



figs. 16-22: British Carb. Brach., p. 124, pi. 26, fig. 1, pi. 27, figs. 1-5, and pi. 30, 



figs. 14-16: Winchell (1862); Proceed. Acad. Nat. Sci., p. 410: and of many other 



authors. 



Shell strongly resupinate, semi-oval, or truncato-sub-circular, being 

 wider than long, with a regularly rounded anterior outline, and lateral 



* In accordance with a suggestion in Vol. I., Part IL, of the Ohio Geological Re- 

 ports, I retain here, provisionally, the name Hemipronites in a subgeneric sense under 

 Strophomena, until the question in regard to the particular group for which the latter 

 name will have to stand has been more satisfactorily settled. Whether certain allied 

 types should be treated as representing distinct genera, or only groups bearing the 

 relations of subgenera of one genus, is often, however, a mere matter of fancy. For 

 the Hemipronites group the name Orthotetes, Fischer, has been recently retained; but 

 it seems to me that this can scarcely be properly done, for the following reasons : 



In the first place, Fischer, in 1829, read a communication from a Mr. Evans before 



