SPIRIFER 327 



an identification, which has doubtless been made because of the strong 

 median plication of the sinus ; the two species, however, are totally differ- 

 ent, S. legrandens'is having a high cardinal area, while 8. biplicatus has a 

 low one, and the cardinal extremities are never extended into the ex- 

 tremely attenuated points in S. legrandensis as they are in 8. biplicatus. 

 There is no species of Spirifer in any of our Mississippian faunas which 

 can be compared with this one. It resembles, however, 8. macbridei Calvin, 

 from the Upper Devonion fauna at Rockford, Iowa, but it is proportionally 

 much broader, with a more nearly flat cardinal area, and has a larger num- 

 ber of plications. It also resembles 8. bimesialis Hall, also from the Upper 

 Devonian of Iowa, but it attains a larger size with a somewhat higher 

 area and more incurved beak, and in the mature shell it often has a pair 

 of lateral plications in the sinus in addition to the strong median one. 

 Horizon. Kinderhook. 



SPIRIFER SUB/EQUALIS Hall 

 Plate XLIII, Figs. 1-10 



1858. Spirifer subequalis Hall, Geol. Iowa, vol. 1, pt. 2, p. 663, pi. 23, 



figs. 9a-c. 

 1883. Spirifer subcequalis Hall, Rep. N. Y. State Geol. for 1882, pi. (31) 



56, figs. 13-14. 



1894. Spirifer subcequalis Hall and Clarke, Int. to Study of Brach., pt. 2, 



pi. 27, fig. 2. 



1895. Spirifer subcequalis Hall and Clarke, Pal. N. Y., vol. 8, pt. 2, pi. 31, 



figs. 13-14. 



1906. Spirifer subcequalis Beede, 30th Ann. Rep. Geol. Survey Ind., p. 

 1316, pi. 21, figs. 3-3b. 



Description. Shell above medium size, much wider than long, the great- 

 est width along the hinge-line, the cardinal extremities acutely angular. 

 The dimensions of a nearly perfect individual are : length of pedicle valve 

 29.8 mm., length of brachial valve 23.5 mm., greatest width, along the 

 hinge-line 60 mm., thickness 23 mm., height of cardinal area 5.5 mm. 



Pedicle valve most convex posterior to the middle, the surface sloping 

 with a gently convex curvature from the umbonal region nearly to the 

 cardinal extremities where it becomes a little compressed, to the cardinal 

 margin the surface slopes with a short and rather abrupt curvature, es- 

 pecially near the beak, the slope to the anterior and antero-lateral mar- 

 gins long and regularly curved; beak small, pointed and moderately in- 

 curved ; mesial sinus shallow, rounded in the bottom, of moderate width, 

 ill-defined laterally; cardinal area concave, becoming more curved to- 

 wards the beak, the lower and more flattened portion lying at an angle of 

 about 65 degrees to the plane of the valve, the lateral margins sharply 

 defined and sloping with a gently convex curvature from the beak to the 

 cardinal extremities, the surface marked by vertical stride. Surface of 



