PLATE IXa— Continued. 

 Fig. 14. A iiiiclinal view of the specimen lllustiated on jJate ix, tig. 1. 



Ti-enton limestone. New York. 

 Fig-. 1.1. An enlarged view of the interioi- of a pedicle-valve ; showing the vascular markings, which are 

 rarely seen in this sjiecies. 



Hudson River group. Wayiiestnlle, Ohio. 



StROPIIOMENA ? (StKOPHONELLA ?) PATENTA, Hall. 



(The actual relations of thi.s species to Strophomena and Strophoxkli.a 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. 



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



Genus ORTHOTHKTES, Pander. 



Page 253. 



ORTnOTHETES SUBPLAXA, Coiinul. 



(See Plate IX, figs. 21-2!t.) 



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

 ment of the ileltidial callosity, the rounded, somewhat unequal lobes of the cardinal process, 

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



Niagara group. Waldron, Indiana. 



Orthoxhetes in^qualis,* Hall. 



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



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

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



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

 ently distingnished fi-om the cruial plates. 



Waverly group (Kinderhook). Burlington, Iowa. 



Orthothetes iNFLATUS, Wliitc iintl Whitfield. 



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

 showing the impression of the cardinal proce.ss and adductoi- muscles. 



Fig. 25. The cardinal process, enlarged tVom a gutta-pei'cha impression ; showing its appearance on the 

 anterior face. The crural bases (x) appear very abiujit at the tcrmin.ition on a<'Count of the 

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

 Waverly group (Kindei-hook). Burlington. Iowa. 



Orthothetes desideratus, ii. sp. 



Fig. 26. A view of the brachial valve of an internal ca.st ; showinfr the muscular impi'essions. 

 Fig. 27. A cai'dinal view of the same specimen. 



Waverly group. Ohio. . I   ", 



• The reference to thi.'j jjpocies in the Report of tlie New York State Geolo^i.st for ISS2, explanalion of plate xi A (= Ix A) 

 as Streplorhynchus aquivalvia, is erroneous. The Bholl is tlie Ortliis itiequali), Hull, Geol. Rep. ol' Iiiwa, p. 490, plate ii, ngs. 

 6, a, b, c. 



