EXPLANATION OF PLATE IV. 



FigS. 1-2. SCHELLWIENELLA BURLINGTONENSIS n. Sp ..p. 67 



1. View of a large, partially exfoliated pedicle valve. 2. View of 

 a smaller, somewhat crushed brachial valve. Cotypes (W M 

 No. 13354.) 



Burlington limestone, Henderson County, Illinois. 



Figs. 3-5. STREPTORHYNCHUS TENUICOSTATUM n. sp p. 69 



3-4. Pedicle and brachial views of a nearly complete example. 

 5. View of an exfoliated brachial valve. Cotypes (W M 

 No. 9665.) 



Chouteau limestone, Chouteau Springs, Missouri. 



Fig. 6. SCHELLWIENELLA ALTERNATA n. sp p. 66 



View of a nearly complete but somewhat exfoliated brachial valve, 

 the holotype. (W. M., No. 13355.) 



Burlington limestone, Burlington, Iowa. 



Figs. 7-12. SCHELLWIENELLA INFLATA (White & Whitfield) p. 59 



7-9. Pedicle, lateral and brachial views of a sulphur cast of one of 

 the cotypes. (W. M., No. 14218.) 



Kinderhook, Bed No. 6, Burlington, Iowa. 



10. View of an internal cast of a nearly complete brachial valve. 

 (W. M., No. 13355.) 11-12. Brachial and lateral views of a 

 nearly complete internal cast of a brachial valve, one of the 

 cotypes. (U. M., No. 1353.) 



Kinderhook, Bed No. 7, Burlington, Iowa. 



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