308 SYSTEMATIC PALEONTOLOGY 



Genus RAPHISTOMINA Ulrich and Scofield 

 BAPHISTOMINA LAUKENTINA (Billings) 



Plate XXXVI, Figs. 6, 7 



Pleurotomaria laurentina Billings, 1859, Canadian Nat. Geol., vol. iv, p. 354, 

 fig. 6. 



Description. Shell 25 to 50 mm. in diameter, lenticular with depressed 

 spire consisting of five or six Avhorls slightly convex on their upper sides, 

 but with a shallow concave band just within their outer margin. Lower 

 .side of body whorl somewhat concave just beneath the margin, then 

 moderately convex to the umbilicus within which it is rather narrowly 

 rounded. Umbilicus deep and about one-fourth the diameter of the 

 shell. The cast of the interior exhibits an acutely rounded margin, 

 which, owing to the concave band above, appears to be turned a little 

 upward, or to have a narrow ridge all around on its upper side. Aperture 

 subrhomboidal, somewhat indented by the adjacent whorl. 



The Appalachian Valley specimens are poorly preserved, but agree in 

 all essential details with the figures of the Canadian specimens published 

 by Billings. 



Occurrence. BEEKMANTOWN LIMESTONE (Ceratopea zone). Stouf- 

 ferstown, Pennsylvania, and east of Williamsport, Maryland. 



Collection. TJ. S. National Museum. 



Genus OMOSPIRA Ulrich 

 OMOSPIKA ALEXANDKA (Billings) 



Plate XLIII, Figs. 16, 17 



Murchisonia Alexandra Billings, 1865, Geol. Surv. Canada, Pal. Fossils, 



vol. I, p. 172. 

 Omospira alexandra Ulrich and Scofield, 1897, Geol. Minnesota, vol. iii, pt. 2, 



p. 946, pi. Ixx, figs. 66, 67. 



Description. " Shell rather large, turbinate, acutely conical ; apical 

 angle from 45 to 50 ; whorls about six, strongly ventricose, with a flat 

 band in the upper third. The aperture appears to be large and ovate; 



