SPIRIFERINA 295 



Brachial valve less convex than the pedicle, most convex posterior to 

 the middle, the surface curving rather abruptly to the cardinal margin 

 and gently to the anterior margin, somewhat compressed towards the 

 cardinal extremities; mesial fold only moderately elevated above the 

 general surface of the valve, originating at the beak, sharply defined, 

 rounded on top ; beak very small, scarcely or not at all extended beyond 

 the cardinal margin; cardinal' area very narrow; the lateral slopes 

 marked by plications similar to those of the opposite valve and alternate 

 with them. Internally the cardinal process is small and inconspicuous, 

 the crural plates are rather strong with the dental sockets excavated 

 from their outer surfaces; the muscular scars are narrow and deeply 

 excavated, with a thickened, marginal, bordering ridge on each side 

 which continues to the anterior margin of the valve. 



Surface of each valve, in addition to the plications, ornamented by 



fine but strong, regular, sublamellose, imbricating, concentric markings 



'which are finely but distinctly fimbriate, from three to four of these 



markings occupy the space of one millimeter. Shell structure minutely 



and closely punctate. 



Remarks. This species has been rarely recognized since its original 

 description without illustrations, by McChesney. It is not an uncommon 

 form from the "Button Mould Knobs" of Kentucky, but its horizon 

 is Kinderhook rather than Kaskaskia, as stated by McChesney. The 

 species is the largest member of the genus in the faunas here considered, 

 and also differs fromj all the other of our species, except 8. subtexta, in the 

 finely fimbriate concentric markings of the shell. 



Horizon. New Providence shale of Kinderhook, Button Mould Knobs, 

 Kentucky. 



SPIRIFERINA NOR WOOD AN A (Hall) 

 Plate XXXVI, Figs. 41-48 



1856. Spirifer norwoodana Hall, Trans. Albany Inst., vol. 4, p. 7. 



1882. Spiriferina Norwoodana Whitfield, Bull. Am. Mus. Nat. Hist., vol. 1, 



p. 48, pi. 6, figs. 16-17. 



1883. Spiriferina norwoodana Hall, 12th Ann. Rep. Geol. Surv. Ind., 



p. 327, pi. 29, figs. 16-17. 



1906. Spiriferina norwoodana Beede, 30th Ann. Rep. Geol. Surv. Ind., p. 

 1311, pi. 22, figs. 16-17. 



Description. Shell small, subsemielliptical in outline, wider than long, 

 the hinge-line a little shorter than the greatest width of the shell, the 

 greatest width posterior to the mid-length of the shell, the cardinal ex- 

 tremities rounded. The dimensions of a nearly perfect specimen are: 

 length of pedicle valve 3.1 mm., length of brachial valve 3 mm., width 

 4 mm., length of hinge-line 3.1 mm., thickness 2.8 mm., height of cardinal 

 area .8 mm., width of sinus in front 1.4 mm. 



