Maryland Geological Survey 685 



shell ■\vitli four or five volutions wlien entire, but seldom preserving more 

 than three — the apex being usually imperfect. The outer volution 

 usually ventricose and regularly convex, a little depressed below the 

 suture-line (but not canaliculate). Aperture suborbicular in perfect 

 specimens, sometimes subrhomboidal ; outer lip thin, with a sharp entire 

 margin; columnar lip thickened, folded, and reflexed over the umbilicus, 

 which in adult specimens is entirely closed. Surface marked by fine, 

 nearly equidistant, thread-like revolving striae, which are cancellated by 

 fine concentric strife of about the same strength, but unequally distant; 

 the latter sometimes bent abruptly backwards upon the back of the shell, 

 indicating a sinus in the lip at some period of growth, and are frequently 

 crowded in fascicles giving a rugose character to the surface. In well- 

 preserved specimens the surface is beautifully cancellated; and in worn 

 and partially exfoliated specimens some remains of these surface mark- 

 ings are usually visible, the revolving strite being first obliterated." Hall, 

 1879. 



Height S mm.; diameter 15 mm. 



The individual figured is somewhat distorted by pressure. The surface 

 is ornamented by numerous fine radiating striaa which curve backward 

 near the periphery and are crossed by finer revolving stride causing the 

 surface of the shell to appear finely cancellated. 



Occurrence. — Jennings Formation, Chemung Member. Upper 

 Tropidolephis zone ? near Pennsylvania-Maryland state line west of Green 

 Ridge. 



Collection. — Maryland Geological Survey. 



Suborder PTEROPODA 

 Faitiily CAVOLINIIDAE 



Genus STYLIOLINA Karpinsky 



Styliolina fissurella (Hall) 



Plate LXXI, Pigs. 1-3 



Tentaculites fissurella Hall, 1843, Geol. N. Y., Rept. 4th Dist., p. 180. 

 Styliola fissurella Hall, 1878, Pal. N. Y., vol. v, pt. ii, p. 178, pi. .\xxia, 



figs. 1-33. 

 Styliolina fissurella Clarke, 1885, Bull. U. S. Geol. Survey, No. 16, p. 57. 



