554 GEOLOGY OF OHIO. 



In the previously described forms the last whorl is frequently more 

 or less expanded towards the aperture producing a slightly trumpet 

 shaped peristome. At .Brown's Quarry are found specimens having a 

 maximum transverse diameter of 25 mm. In these the shell is also 

 rapidly expanded towards the aperture, but the peristome is more or less 

 strongly wrinkled perpendicularly to the edge of the lip, the upper edge 

 of the inner lip, however, being adnate to the surface of the previous 

 whorl as heretofore. At Huffman's Quarry, in the upper shaly courses, 

 the end of the last whorl becomes free from the earlier whorls of the 

 shell, and becomes more or less distant from the rest of the shell. The 

 inner lip, therefore, is no longer adnate to the surface of the previous 

 whorl, but assists in forming the more or less strongly angulated peris- 

 tome, wrinkles transverse to the edge of the lip being developed as in 

 the previously described form. On examining the inner lip of these 

 Huffman quarry specimens, it is seen to be twisted, and interiorly, along 

 the line of the twist or fold, a certain amount of thickening has taken 

 place. In these shells with the transversely wrinkled or plicated peris- 

 tome the surface of the last whorl usually shows only transverse striae, 

 the revolving striae being almost obsolete even over most of the remain- 

 ing parts of the shell, though sometimes preserved on the younger whorls. 

 These forms attain a width of 25 mm. 



It does not seem possible to maintain any distinction between the 

 genera Platyceras and Platy stoma. 



Platyceras Niagarense, Var. Clintonense, var. nov. 



(Plate 37a, Pig. 8.) 



In the ferruginous limestone at the top of the Clinton, just under the 

 Onondaga shales, near Mifflintown, Juniata county, Pennsylvania, Prof. E. 

 W. Claypole found a number of specimens of Platyceras of a type quite 

 distinct from those just described. The young are very much after the 

 fashion of the previously described shells excepting that the spire is per- 

 haps more depressed. Two to three of the initial whorls touch each 

 other, after which the succeeding whorls grow loosened from each other, 

 and show a tendency towards a straight growth, the last whorl being of 

 the form of a massive, spirally twisted pillar, in which the coiling is but 

 very moderate. No trace of longitudinal or revolving striae were present. 

 Transverse striae were frequent, but these were broad and flattened, and 

 did not have the sharpness often seen in the ordinary Ohio specimens. 

 It may be distinguished as variety Ctintonense and seems to be the pre- 

 cursor of such forms as Plactyceras spirale, Hall, of the Lower Helder- 

 berg. 



Subulites directvs, sp. nov. 



(Plate 37a, Figs. 5 a, b.) 



Shell elongate, slender, fusiform; some of the specimens are almost 

 straight, most of them however show a very moderate curvature, the 



