PLATE IXa— Continueii. 

 Fig-. 14. A curtiiiial view of the specimen illu.stiated on j)late ix, tig. 1. 



Ti-enton limestone. New York. 

 Fig. 1.5. An enlarged view of the interior of a pedicle-valve ; showing- the vascular mai-king-s. which are 

 rarely seen in this species. 



Hudson River g-ronp. Waynesville, Ohio. 



StROPIIOMENA ? (StROPHONELLA ?) PATENTA, Hall. 



(The actual relations of this species to STRorHOMBNA and Strophonella are not yet fully determined.) 

 Fig. 16. The interior of a large pedicle-valve ; showing the muscular area. 

 Fig. 17. The exterior of the pedicle-valve. 

 Fig. 18. The interior of a smaller pedicle-valve. 



C-'linton gi-oup. Reynale's Basin, N. Y. 



Genus OETHOTHKTES, Pander. 



Page '253. 



Orthothetes subplana, Conrad. 

 (See Plate IX, figs. 21-2ii.) 



Fig. 19. An enlargement of the central cardinal portion of the brachial valve ; showing the gi-eat develop- 

 ment of the deltidial callosity, the rounded, somewhat unequal lobes of the cai-dinal process, 

 and the thin, abi-upt, nearly vertical crural plates. X 3. 

 Niagara group. Waldron, Indiana. , 



Orthothetes in^qualis,* Hull. 



Fig. 20. The interior of a pedicle-valve. 



Fig. 21. A small brachial valve ; showing a tendency to a fasciculation of the striiB. 

 Fig. 22. A cardinal view of an internal cast of the brachial valve. 



Fig. 23. The intei-ior of a bi-achial valve. In this figure the lobes of the cardinal process are not suffici- 

 ently distinguished from the crural plates. 



Wavei-ly gi-oup (Kinderhook). Burlington, lotoa. 



Orthothetes inflatus, White ami Whiltiekl. 



Fig. 24. A cardinal view of one of the original specimens, which is an internal cast of the brachial valve ; 

 showing the impression of the cardinal process and ailductor muscles. 



Fig. 2.5. The cardinal process, enlarged from a gutta-percha impression ; showing its appearance on the 

 anterior face. Tlie crural bases (x) appear very abrupt at the termination on account of the 

 impression having been taken without the shell being first entirely i-emoved from the matrix. 

 Waverly grouji (Kinderhook). Burlington. Iowa. 



Orthothetes desideratus, n. sp. 



Fig. 26. A view of the brachial valve of an internal cast ; showing the muscular impressions. 

 Fig. 27. A caidinal view of the same specimen. 

 Wavei-ly group. Ohio. 



• The reference to this species in the Report of the New York .St.ite GeoloKi.st for 1882, explanation of plate xi A (= IXA) 

 as Slreptorhynchus aquivalvia, is erroneous. The shell is the Orthis inegualis, llall, Geol. Rep. of Iowa, p. iSO, plate ii, ligs. 

 t>, a, b, c. 



