PI-ATE IV K— Continued. 

 LiNOULA LAMELLATA, Hall. 



Fig. 10. View from the jiedicle-valve of an iiitei-nul cast, i-etaining the iini;)res.siori of the lateral and central 

 muscular scai'S ami of the pallia! sinases. The matiix is filled \vith minute ovoid bodies (ova), 

 which appear to be distributed whei'ever the sinuses and Iheir branches have extended. About 

 the anteiior and lateral mai-g-infe of the valve the matrix is the opaque mud of the sediment ; 

 elsewhere the spaces between the ova are translucent. X 3. 



Fig. 11. The opjjosite side of the same sjiecimen ; also showing- the muscular, vasculai' and septal impres- 

 sions. The intermixture of the opaque matiix on this side is somewhat greater than on the 

 other, obliterating the ova to some extent. X 3- 



Fig. 12. A thin section of a poi'tion of this specimen, which shows the ovoid bodies to be opaque and 

 homogenous. X 12 



Fig. 13. An enlargement of the surface of the cast ; showing the appearance of the ova when magnified 12 

 diameters. The vertical ridges ai-e casts of I'adiating furrows on the inteiior of the valve. 

 Niagara group. Near Hamilton, Ontario. 



LINGULOPS, Hall. 



Page 18. 

 LlNGULOPS GrANTI, Sp. IIOV. 

 Fig. 14. The intei-ior of a. bi-achial valve. X 'i- 



Fig. 15. The iriterior of a pedicle-valve. The muscular area is hei'e developed into a well-defined plat- 

 foi m, while in the other sjiecies of the genus, L. TVhitfieldi and L. Norwoodi, it still letains its 

 linguloid character. X 6. 



Niagara group. Hamilton, Ontario. 



COKOTRETA, Walcott. 



Page 104. , 



CONOTRETA EuSTl, WalcOtt. 



Fig. 16. Auterioi' view of a pedicle-valve. The apical and antei-ior i-egions retain a iioi-tion of the shell, 



but elsewhere the shell is removed, showing the impi'essions of the internal radiating muscular 



I'idges. X 4. 

 An inteinal cast of a smaller pedicle-valve ; showing the impression of the sti-ong apical callosity, 



and the i'adiating ridges. X S. 

 An apical view of the same valve ; showing the subti'iangular jiosterioi' slope, and its obscurely 



defiued median furi-ow. X 9. 

 Cardinal view of a vei-y young individual, in which the posterior slope is very faint. X 12. 



Trenton limestone. Trentim Falls, N. Y. 

 Cai-dinal view of another veiy small example, retaining the shell. 



Pi'oHle of same. X 25 



Hudson River group. Covington, Ky. 



OBOLUS, ElCHWALD. 



Page SO. 



Obolus [?J pulcher, Matthew. 



Fig. 22. The extei-ior of a valve, retaining the shell and showing the character of its ornamentation. X 3. 

 St. John gi'oup. Caton's Island, New Bi-un.swick. 



DISCINA, Lamarck. 



Page 120. 



DisciNA STRIATA, Scluiiiiacher. 

 Fig, 23. The interior of a pedicle-valve. 

 Fig 24. The exterior of a similar valve. Much enlarged. 

 Recent. Cape Palmas. 

 (Aftei- David.son. Trans. Linnean Soc, Ser. 2, Zool., vol. iv, pi. 25, tigs. 24, 25. 1889.) 



Fig. 



17, 



Fig. 



IS. 



Fig. 



19. 



Fig. 



20. 



Fig. 



21. 



