418 PROCEEDINGS OF THE ACADEMY OF 



prominent, acute, incurved and turned backward ; cardinal lines nearly 

 straight, beyond the dental series curving rapidly to the extremities, of which 

 the anterior is broadly rounded ; ventral side with a slight general convexity, 

 varied by a broad shallow sinuation in front of the middle, which extends 

 one-third the distance up to the beaks. Pallial line entire ; posterior adductor 

 forming a round deep scar. Cardinal angle between the beaks varying from 

 115 to 125 ; teeth numerous, in a series not perceptibly interrupted between 

 the beaks, those on the anterior slope posteriorly angulated, those on the pos- 

 terior slope rather larger ; the remoter often transverse to the hinge plate ; 

 those nearer the beak angulated forwards ; between the beaks the hinge plate 

 is somewhat widened, and the teeth are slender, long and crowded in a scarcely 

 interrupted series. Shell massive, thickened around the smooth ventral mar- 

 gin ; external surface marked by numerous unequal lines of growth ; casts 

 nearly smooth. 



Length of an average specimen 1-45 (100) ; height *80 (55) ; convexity of 

 one valve -26 (IS) ; length of posterior end '59 (41) ; anterior end -96 (66) ; 

 height of beaks above line connecting extremities *46 (32) ; number of teeth 

 in posterior series from 12 to 16 ; in anterior from 30 to 40. 



Localities. Marshall, Battle Creek, Moscow, and at nearly every other ex- 

 posure of the Marshall Sandstone in the southern part of the State. The 

 most abundant fossil in the group, generally occurring in beds ten or twelve 

 inches in thickness. 



This species has about the proportions of Cucullella tenuiarata, Sandb. 

 (Verstein, 276, Taf. xxix. 4), but specimens of the latter from Kirschweiler, 

 in the cabinet of Dr. Rominger, are more symmetrically furrowed, and pos- 

 sess fewer teeth. 



This is, perhaps, the species described by Dr. Stevens as Leda nuculceformh 

 (Sill. Jour. [2], xxv. 262), but it is not Leda, and the number of teeth is 

 much too great for his description. 



Named in honor of Bela Hubbard, Esq., of Detroit, who published in 1840 

 the first notice on record of the interesting sandstones under consideration, 

 and designated the generic relations of several of the more abundant fossils. 



Var. prolata. A form which I am inclined to regard as only a variety of the 

 preceding, is very ventricose, and more elongated anteriorly, with a greater 

 number of teeth. 



Length 1-46 (100); height *69 (47); convexity of one valve -28 (19); length 

 of posterior end *38 (26); of anterior end 1*06 (72). 



Localities. Moscow and Battle Creek. 



Nccula Iowensis. White and Whitfield (Proc. Bos. Soc. Nat. Hist., Feb. 

 1862, p. 298). Shell small, triangularly ovate, ventricose, with prominent 

 incurved, subterminal beaks. Cardinal plate forming an angle of 95, but the 

 dorsal outline of the shell, from the prominence of the beaks, forms an angle 

 of 80 c . Anterior and posterior slopes truncated ; anterior extremity rounded, 

 ventral border semi-elliptic. Long end with about 11 teeth ; short end with 

 6 very inconspicuous ones. Pallial impression entire, connecting the deep 

 adductor scars ; anterior scar nearly terminal, lenticular, with a small oval 

 scar above ; posterior scar oval, scarcely above the extremity. Shell thickened 

 near the margin. 



Length '47 (100); height '40 (85) ; convexity -26 (55) ; distance from beak 

 to line joining extremities *27 (57). 



Localities. Battle Creek and Sec. 7, Wyoming, Kent county. 



These specimens possess a somewhat greater number of teeth than the Iowa 

 ones, according to the author's description. In general form they recall 

 Cucullaa antiqua, Sow., from the old red sandstone of Felindre (Murch. Sil. 

 Syst., pi. iii. fig. 120). 



Nucula sectoralis, n. sp. Shell rather small, ventricose, sectoriform, with 

 nearly central beaks. Anterior cardinal slope straight ; posterior, nearly so, 



[Sept. 



