SCHELLWIENELLA 61 



the cardinal area is commonly convex. An internal cast of a pedicle 

 valve from the same horizon and locality, probably a member of this 

 species, does not have a distorted beak and has a flat cardinal area which 

 slopes posteriorly from the hinge-line at an angle of about 115 degrees ; it 

 also shows the presence of short but distinct dental plates and a scarcely 

 denned, flabellate muscular sear. 



The pedicle valve of this species, so far as it has been observed, re- 

 sembles that of 8. planumbona, but it is probably more often distorted at 

 the beak than that species and usually has more conspicuous lines of 

 growth. It is probably true, however, that some specimens of the pedicle 

 valve of 8. planumbona, were included by White and Whitfield among the 

 types of this species. The brachial valves of the two species are entirely 

 different, the umbonal region of this one being very prominent and some- 

 what protuberant beyond the cardinal margin, while the same region in 

 8. planumbona is very gently convex, the slope to the anterior margin of 

 the shell being more abrupt than that to the cardinal margin. 



Horizon. Kinderhook. 



SCHELDWIENELLA IN^QUALIS (Hall) 



Plate III, Figs. 14-16 



1858. Ortkis inequalis Hall, Geol. Iowa, vol. 1, pt. 2, p. 490, pi. 2, figs. 6a-c. 

 1865. Streptorhynchus inequalis "Winchell, Proc. Acad. Nat. Sci., Phil., 



p. 117. 

 1870. Hemipronites inequalis Winchell, Proc. Am. Phil. Soc., vol. 11, 



p. 251. 

 1877. Streptorhynchus equivalvis Hall and Whitfield, U. S. Geol. Expl., 



40th Par., vol. 4, p. 252, pi. 4, figs. 1, 2. 

 1883. Streptorhynchus cequivalvis Hall, Rep. N. Y. State Geol. for 1882, 



pi. (11A) 42, figs. 20-23. 

 1892. Orthothetes incequalis Hall and Clarke, Pal. N. Y., vol. 8, pt. 1, 



pi. 9A, figs. 20-23. 



1899. Orthothetes incequalis Girty, Mon. U. S. Geol. Survey, vol. 32, p. 522, 



pi. 68, fig. 3a. 



1900. Orthothetes incequalis Weller, trans. St. Louis Acad. Sci., vol. 10, 



p. 66, pi. 1, fig. 18. 



1901. Orthothetes incequalis Weller, Trans. St. Louis Acad. Sci., vol. 11, 



pp. 159 and 195, pi. 14, figs. 16-18, and pi. 19, fig. '9. 



1903. Orthothetes incequalis Girty, Prof. Paper U. S. Geol. Survey No. 16, 

 p. 276. 



Description. Shell concavo-convex, of about medium size, wider than 

 long, the greatest width near or in front of the mid-length, the hinge-line 

 a little shorter than the greatest width, the cardinal extremities angular. 

 The dimensions of a large, nearly complete pedicle valve are: length 23.7 

 mm., greatest width 31.4 mm., length of hinge-line 30 mm. The dimen- 

 sions of a brachial valve are : length 18.5 mm., width 22 mm., length of 

 hinge-line 18.5 mm., convexity 6.5 mm. 



