MARYLAND GEOLOGICAL SURVEY 289 



Genus ORTHODESMA Hall and Whitfield 



ORTHODESMA NASUTUM (Conrad) 



Plate LVIII, Fig. 1 



Cypricardites nasuta Conrad, 1841, 5th. Ann. Kept. New York Geol. Surv., 



p. 52. 

 Modiolopsis nasutus Hall, 1847, Pal. New York, vol. i, p. 159, pi. xxxv, fig. 7, 



p. 296, pi. Ixxxi, fig. 2. 

 Orthodesma nasutum Foerste, 1914, Bull. Sci. Lab. Denison Univ., vol. xvii, 



p. 286, pi. iii, fig. 5; pi. 5, fig. 3. 



Description. This well-marked species is easily distinguished from all 

 associated pelecypods by its narrow, subelliptical form and its anterior 

 extremity drawn out into a narrow, quite extended nasute form. The 

 cardinal margin of the shell is distinctly straight posterior to the beak, 

 but anterior to it the margin drops so that at its greatest departure it is 

 at least 3 mm. lower. In its anterior portion the shell is depressed and 

 this, in connection with the outline, adds to the nasute appearance. 

 Posterior to the beak the shell is more convex with the areas of greatest 

 convexity near the cardinal margin. The surface is marked by indistinct 

 concentric striations which are plainest along the basal margin of the 

 anterior part. 



The type specimens were secured from the Pulaski shale division of 

 the Lorraine at Lorraine, near Borne, etc., New York. 



Occurrence. MARTINSBURG SHALE (Fairview division). Tuscarora 

 Mountain, one and one-half miles southeast of McConnellsburg, Penn- 

 sylvania. 



Collection. U. S. National Museum. 



CLASS GASTROPODA 

 order ASPIDOBRANCHIA 



Family PLEUROTOMARIIDAE 



Genus PLEUROTOMARIA Defrance 



PLEUROTOMARIA ? CANADENSIS Billings 



Plate XXXVI, Figs. 4, 5 



Pleurotomaria canadensis Billings, 1865, Pal. Fossils, vol. i, Geol. Surv. 

 Canada, p. 230, figs. 214, a, b. 



