SPIRIFER 357 



marked by plications similar in form and number to those of the opposite 

 valve ; the lateral slopes marked by plications similar in all ways to those 

 of the opposite valve. 



The minute surface markings of the shell are not preserved in the con- 

 dition of preservation in which all the examples have been found. Some 

 concentric lines of growth of greater or less strength occur at irregular 

 intervals. 



Remarks. This species has been observed only in the condition of in- 

 ternal casts in a fine-grained sandstone, a condition in which the more 

 minute markings of the shell cannot be recognized. It is therefore im- 

 possible to determine whether or not the shell was marked by minute 

 longitudinal striae or corrugations such as are present in 8. grimesi, 8. 

 iogani, and S. striatiformis. In its completely plicated shell with similar, 

 bifurcating plications on both fold and sinus and on the lateral slopes of 

 the valves, the species resembles the above named forms, but it differs 

 essentially from all of these in its size and proportions. 



Hall's original designation of the species, S. subrotundatus, proves to 

 have been preoccupied by McCoy, in consequence of which it is here 

 called 8. subrotundus. 



Horizon. Chonopectus sandstone of the Kinderhook. 



SPIRIFER MAPLENSIS n. sp. 

 Plate LI, Figs. 3-8 



Description. Shell of medium size, usually longer than wide, and longi- 

 tudinally subelliptical in outline, but occasionally individuals occur in 

 which the length and breadth are nearly equal; the hinge-line shorter 

 than the greatest width of the shell, the cardinal extremities rounded. 

 The dimensions of a medium sized pedicle valve are: length 29 mm., 

 width 22 mm., convexity 10 mm., length of hinge-line 14 mm. The dimen- 

 sions of a brachial valve are: length 25 mm., width 21 mm., convexity 6 

 mm. The dimensions of the largest example observed, a pedicle valve, 

 are : length 37 mm., width 37 mm., convexity 16 mm. 



Pedicle valve strongly and regularly convex, the convexity extending 

 out to the cardinal extremities, the greatest convexity near or posterior 

 to the middle ; beak obtuse in the internal casts, reaching but a short dis- 

 tance back of the hinge-line; character of the cardinal area not well 

 shown in the specimens, but it is evidently low and small ; lateral slopes 

 of the valve sloping abruptly with a convex curvature from near the 

 mesial sinus to the lateral margins, the surface becoming nearly vertical 

 to the plane of the valve near the margin, the curvature to the cardinal 

 margin more abrupt than to the lateral margin, each lateral slope marked 

 by from 20 to 25 flattened, radiating plications which increase by bifur- 

 cation in passing towards the anterior margin, and decrease in size to- 



