PLATE XLIX 



PAGE 



Fig. 1. STROPHOMENA SCULPTURATA Bassler n. sp 250 



Exterior of a brachial valve illustrating the highly ornamented sur- 

 face. X 2. 



Ordovician (Mohawkian), Sinuites bed at base of Martinsburg 

 shale, 1 mile south of St. Thomas, Pennsylvania. 



Fig. 2. LEPTAENA TENUISTRIATA Sowerby var 260 



Pedicle valve of an incomplete specimen. X 2. 



Ordovician (Mohawkian), Sinuites bed at base of Martins- 

 burg shale, 1 mile south of St. Thomas, Pennsylvania. 



Figs. 3-10. CHRISTIANIA LAMELLOSA Bassler n. sp 257 



3, 4. Pedicle valve showing the characteristic lamellose markings. 



Natural size and X 2. 



5, 6. Another example showing pedicle valve, natural size and X 2. 

 7, 8. Brachial valve of another specimen natural size and X 2. 

 9, 10. Interior of a brachial valve illustrating characteristic muscular 

 scars. Natural size and X 2. 



Ordovician (Mohawkian), base of Martinsburg shale, Stras- 

 burg, Virginia. 



Figs. 11-13. TRIPLECIA (CLIFTONIA) SIMULATRIX Bassler n. sp 266 



11. Pedicle valve of an exfoliated specimen. 



Ordovician (Mohawkian), Sinuites bed at base of Martins- 

 burg shale, 1 mile south of St. Thomas, Pennsylvania. 

 12, 13. Brachial valve with the shell preserved. Natural size and 

 enlarged. 



Ordovician (Mohawkian), base of Martinsburg shale, Stras- 

 burg, Virginia. 



Figs. 14-16. LEPTOBOLUS ? OVALIS Bassler n. sp 230 



14. Exterior of pedicle valve. X 4. 



15. Interior of brachial valve showing the median and lateral septa. 



X4. 



16. Interior of another brachial valve with markings more obscure. 



X4. 



Ordovician (Mohawkian), Sinuites bed at base of Martinsburg 

 shale, 2 miles northwest of Kauffman, Pennsylvania. 



Figs. 17-21. DALMANELLA EDSONI Bassler n. sp 243 



17. Interior of brachial valve. 



18. Pedicle valve of incomplete specimen illustrating the strongly 



marked ridges. 



19. Brachial valve of specimen almost complete. 



Sinuites bed at base of Martinsburg shale 1 mile south of 

 St. Thomas, Pennsylvania. 



20. Brachial valve of partially exfoliated example. 



21. Exfoliated and incomplete pedicle valve. 



Ordovician (Mohawkian), Trenton limestone, Shipyard Bay, 

 Highgate Springs, Vermont. 



Figs. 22, 23. COLEOLUS IOWENSIS James 320 



22. Rock fragment with numerous specimens illustrating the long, 



slender curved form. X 2. 



23. Portion of the same showing exterior of shells. X 6. 



Richmond group, Maquoketa shale, Graf, Iowa. 



399 



