296 MISSISSIPPIAN BRACHIOPODA 



Pedicle valve strongly convex, most prominent near the umbo, the 

 surface curving abruptly to the cardinal margin and more gently to 

 the lateral and anterior margins, sometimes slightly compressed towards 

 the cardinal extremities ; mesial sinus originating at the beak, of moderate 

 width and depth, rounded in the bottom; beak small, pointed or mod- 

 erately blunt, incurved ; cardinal area small, concave, the lateral margins 

 ill-defined, rounding into the lateral slopes of the valve ; delthyrium about 

 as wide as high ; each lateral slope marked by from three to five, simple, 

 rounded plications, which originate at or near the cardinal margin, 

 those bounding the mesial sinus are much the stronger, the last ones 

 towards the cardinal extremities being very faint or almost obsolete. 

 Internally, the median septum is reduced to a slight ridge which extends 

 anteriorly from the beak for about one-third the length of the valve, the 

 dental plates are weakly developed, being little more than a thickening 

 of the valve along the inner margin of the delthyrium. 



Brachial valve less convex than the pedicle, the greatest convexity 

 posterior to the middle, the surface a little compressed towards the 

 cardinal extremities ; mesial fold well defined, rounded, but little elevated 

 above the general surface of the valve, sometimes with a slight mesial 

 depression towards the front ; beaks very small and incurved ; the cardinal 

 area very narrow; plications similar to those of the opposite valve and 

 alternate with them. 



Surface of both valves, when well preserved, marked by minute papilke. 

 Towards the front of the shell one or more concentric lines of growth 

 are frequently present. Shell structure minutely punctate. 



Remarks. The specimen whose dimensions have been given above is 

 one of the largest members of the species which has come under obser- 

 vation of the writer. The type specimens of the species, however, include 

 somewhat larger individuals, the maximum dimensions recorded by Hall 

 being length 4.5 mm. and width 5.25 mm. The species has been compared 

 \vith 8. spinosa by Whitfield, who seems to have held the opinion that it 

 might be only a diminutive form of that species. It resembles 8. spinosa 

 in the surface ornamentation of the shell, but besides being so much smaller, 

 8. nonvoodana is more rounded at the cardinal extremities, has a much 

 less sharply defined cardinal area, and more broadly rounded plications, 

 and it is believed that the two forms are clearly distinct specifically. 



Horizon. Salem limestone. 



SPIRIFERINA SALEMENSIS n. sp. 

 Plate XXXVI, Figs. 1-5 



Description. Shell below medium size, broader than long, the greatest 

 width along the hinge-line, the cardinal extremities angular. The dimen- 

 sions of a nearly perfect specimen are : length of pedicle valve 16.3 mm., 



