530 Systematic Paleontology 



and the general neatness of form, imparts a striking elegance to the shell. 

 The depth of the anterior sulcus, whicli, however, is located very near the 

 middle of the valve, is somewhat suggestive of Primitiidag like Eurychilina. 

 But the size and form of the median lobe — indeed every feature that ex- 

 perience has shown to be essential — is too thoroughly in accord with 

 KJocdenia to have any doubt as to the generic position of the species. Only 

 a few specimens have been seen and none of these have a ventral pouch. 



Length of left valve, including marginal spines, 2.5 mm.; width 1.3 

 mm. : height 0.5 mm. 



This species was described from the Coeymans limestone of Herkimer 

 County, New York, and fragments of apparently the same form have been 

 noted at Cumberland, Maryland. 



Occurrence. — Helderbeeg Formatiox, Keysek Meaibeu. Cumber- 

 land. 



Collection. — U. S. National Museum. 



Klcedexia neaepassi (Weller) 

 Plate XCVII, Figs. 12, 13 



Beyrichia nearpassi Weller, 1903, Geol. Surv. N. J., Pal., vol. ill, p. 255, pi. 



xxiii, figs. 7, 8. 

 Klocdenia nearpassi Ulrich and Bassler, 1908, Proc. U. S. Nat. Mus., vol. xxxv, 



p. 301 (gen. ref.). 



Description. — " Carapace subelliptical in outline, the posterior ex- 

 tremity equaling or a little narrower than the anterior; the hinge-line 

 straight, about four-fifths of the total length of the valves. Free margin, 

 with a flattened, marginal border. Valves divided into three lobes by two 

 rather broad and deeply impressed, nearly equal furrows, which start from 

 the dorsal margin and extend vertically downward to about the middle 

 of the valve. A shallower and less sharply defined furrow extends verti- 

 cally upward from the ventral margin, directly beneath the anterior 

 furrow from the dorsal margin, the two being indefinitely connected 

 across the middle of the valve by a slight depression. The posterior lobe 

 is strongly convex and is the largest of the three, occupying about one-half 

 of the total length of tlie valve; medial lobe subglobular, about as high as 



