I'LATE IXA— Continued. 

 Fig. 14. A cardinal view of the specimen illustrated on plate ix, fig. 1. 



Trenton limestone. New York. 

 Fig. 15. An enlarged view of the interioi- of a pedicle-valve ; showing the vascular markings, which are 

 rarely seen in this species.. 



Hudson River group. Waynesville, Ohio. 



StEOPHOMENA ? (StROPHONELLA ?) PATENTA, Hall. 



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

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

 Fig. 17. The extei'ior of the i:iedicle-valve. 

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



Clinton group. Reynale's Basin, N. Y. 



Genus ORTHOTHKTES, Pander. 



Page 253. 



Orthothetes subplana, Conrad. 

 (See Plate IX, figs. 21-29.) 



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

 ment of the deltidial callosity, the I'ounded, somewhat unequal lobes of the cardinal process, 

 and the thin, abrupt, nearly vertical crural plates. X 3. 

 Niagara group. Waldron, Indiana. 



Orthothetes in^qualis,* Hall. 



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



Fig. 21. A small bi'achial valve ; showing a tendency to a fasciculation of the sti-iae. 

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



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

 ently distinguished from the crural plates. 



Wavei-ly group (Kinderhook). Burlington, Iowa. 



Orthothetes inflatus. White and Whitfield. 



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 cai'dinal process and adductor muscles. 



Fig. 25. The cai'dinal process, enlarged from a gutta-percha impression ; showing its appearance on the 

 anterioi' face. The crural bases (x) appear very abrupt at the termination on account of the 

 impression having been taken without the shell being tii-st entirely removed fi-om the matrix. 

 Waverly group (Kinderhook). Burlington, Iowa. 



Orthothetes desideratus, n. sp. 



Fig. 26. A view of the bi'achial valve of an internal cast ; showing the muscular impressions. 

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

 Waverly group. Ohio. 



* The reference to this species in the Report of the New York State Geologist for 1S82, explanation of plate xi A (= ix A) 

 as Streptorhynchus cequivalvU, is erroneous. The shell is the Orthis ineqitalis. Hall, Geol. Rep. of Iowa, p. 490, plate ii, figs. 

 6, a, b, c. 



