290 SYSTEMATIC PALEONTOLOGY 



Description. Shell large, lenticular 35 to 60 mm. in diameter, consist- 

 ing of six somewhat slender whorls rising into a depressed conical spire. 

 Inner two-thirds of whorls gently convex; suture distinct. Margin of 

 whorls sometimes acute and turned upwards, sometimes with a rounded 

 band. Just within the margin is a wider concave band. Umbilicus wide, 

 one-half to two-thirds the shell diameter, with margin subangular, and 

 the inner slope of the whorls generally flat. A slight concave band just 

 beneath the margin on the under side of the whorls. Aperture trans- 

 versely ovate or rhomboidal with the outer and inner angles acute. Sur- 

 face with fine, sharp, unequal striae, usually with shallow undulations 

 2 to 4 mm. wide conforming to the coarse of the striae ; all curving back- 

 wards to the margin and reaching it at an acute angle. 



Occurrence. BEEKMANTOWN LIMESTONE (Ceratopea zone). Near 

 McConnellsburg and other localities in southern Pennsylvania and east 

 of Williamsport and near Halfway, Maryland. 



Collection. TJ. S. National Museum. 



PLEUKOTOMAKIA ? GEEGAEIA Billings 

 Plate XXXV, Figs. 1-3 



Pleurotomaria gregaria Billings, 1859, Canadian Nat. Geol., vol. iv, pp. 355, 

 358, figs. 8h-k. 



Description. Shell small, 8 mm. long and 5 mm. wide; spire conical 

 with an apical angle of about 45 ; three or four whorls. A narrow spiral 

 band is present. On the body whorl, the band is somewhat above the 

 middle of the volution, but in the upper whorls it is situated on the lower 

 outer side at about one-fourth the height. An obscure carina on the body 

 whorl, just above the spiral band, and another close to the suture is 

 present on mature examples; the intervening space is flat or slightly con- 

 cave. Below the band is a third carina, scarcely visible, and below this 

 the whorl is rounded ventricose. There is a small umbilicus. Surface 

 minutely striated. 



This is an interesting and well-marked species, but until a complete 

 revision of Beekmantown gastropods is made, its generic position must 

 remain very uncertain. 



