248 POTTS VILLE FAUNA OF OHIO 



Genus Pharkidonotus Girty 



Pharkidonotus percarinatus (Conrad) 

 PI. XV, fig. 6 



1842 Bellerophon percarinatus. Conrad, Jour. Acad. Nat. Sci. Phil., 1st Ser., Vol. 

 VIII, p. 268, PL XVI, Fig. 5. 



Carboniferous: Inclined plane of the Allegheny Mts., in black shale over- 

 lying the stratum of Coal No. 7. 



1915 Pharkidonotus percarinatus. Girty, U. S. Geol. Surv., Bull. 544, p. 165, PL XIX, 

 Figs. 4-9c. 

 Wewoka formation: Oklahoma. 



Description. This is undoubtedly the most common and widely 

 distributed gastropod of the Lower Mercer and McArthur limestones, 

 but has not been found below the former horizon. It is easily dis- 

 tinguished by the coarsely nodose carina which occupies the median 

 line of the dorsum, and by the large angular transverse plications on 

 either side of the carina. As the form grades toward the variety tri- 

 carinatus a row of lateral nodes becomes more or less well developed on 

 both sides of the median nodose carina. Many of the specimens here 

 assigned to P. percarinatus show the lateral nodes somewhat developed 

 and are really intermediate between P. percarinatus and the variety 

 tricar inatus. 



Horizon and locality. Widely distributed throughout the Lower 

 Mercer and McArthur members, c. 



Pharkidonotus percarinatus var. tricarinatus (Shumard) 



1855 Bellerophon percarinatus. Norwood and Pratten, Jour. Acad. Nat. Sci. Phil., 



2nd Ser., Vol. Ill, p. 74, PL IX, Figs. 4 a-c. 



Coal Measures: Grayville, Illinois; Posey County, Indiana; and 5 miles 



below New Harmony, Indiana. 

 1858 Bellerophon tricarinatus. Shumard, Trans. St. Louis Acad. Sci., Vol. 1, p. 204. 



Upper Coal Measures: Kansas. 



Description. Pharkidonotus percarinatus var. tricarinatus differs 

 from P. percarinatus in having a row of well developed, prominent 

 nodes occupying the transverse wrinkles on either side of the median 

 nodose carina, so that three rows of nodes are present on the dorsum. 

 The development of the lateral nodes is a very variable character, and 

 differs markedly between young and old specimens, as well as between 

 individuals of the same age so that there is a series of forms grading 

 gradually from one variety to the other. Only those forms with promi- 

 nently developed lateral nodes are here assigned to the variety tri- 

 carinatus, although some of the intermediate forms may possibly belong 



