REPORT OF THE STATE PALEONTOLOGIST I903 247 



width and concavity respectively ; that of the pedicle valve is 7mm 

 by 9mm by 3mm. 



This species is very similar to S . c r i s p u s of the Niagara 

 group as shown by a comparison of Hall's figures and the following 

 measurements : 



fa O Jh ^ ^ 



Oh j o o 



2 w K o ^' 2 



^ faC«« 



X H f-* ^ a: O ^^ 



S. vaniLvemi from Trilohite mountain, N. Y. 



6 S 1 . 34 2 Brachial valve ) . 



"^ - . V Average size 



7 10 1.43 3 Pedicle valve j 



10 12 1.2 5 Pedicle valve very convex 

 S. crispus, Niagara shale, Waldron Ind} 



12 15 1. 21 4 Pedicle valve ; 



11 15 1.36 3 Brachial valve 



S. crispus from Rochester shale, Niagara gorge, N. Y} 



5.5 9 1.64 3 Pedicle valve ") Shells of this size are 

 4.5 92 2 Brachial valve j very abundant 



As seen from the above comparisons and figures,^' ^ S . v a n u - 

 X e m i bears a closer resemblance to S. crispus of Waldron 

 than it does to the Niagara gorge species. This similarity is spec- 

 ially noticed in the proportion of length to breadth and in the num- 

 ber of plications. The Waldron shells are also much more gibbous 

 and thus approach S . v a n u x e m i more nearly than do the 

 Niagara gorge specimens. But the cardinal area is much higher 

 even in the young of all specimens of S . crispus examined 

 than in any of .S . v a n u x e m i . It is thus seen that while S . 

 vanuxemi is apparently much more closely related to the 

 western S . crispus than it is to the eastern, that its possible 

 derivation from the western species could not have been a direct one. 



^These measurements are from specimens in the paleontologic collec- 

 tions of Columbia University, New York. 

 -S. crispus. Pal. N. Y. 2 1262, pi. 54, fig.3a-k. 

 'S. vanuxemi. Pal. N. Y. 3:198, pl.8, fig.17-23. 



