PLATE VIII. 



(Figures 1-18, 22-31 by E. P. Whitfield; 20, 21 by F. J. Swinton; 19 by G. B. Simpson.) 



Legend. D. Deltiilium, pedicle-valve. b. Dental sockets. 

 C. Dcltidiiim, l)rjichial valve. t. Teeth. 



^. Uelthyiium. j. Cardinal pi'ocess. 



F. Foramen. a. Adductor scare. 



F'. Groove on deliliyiiiim, brachial valve. r. Anterior diductor scars. 



A. Cardinal ai'ea : r'. Postenor diductor scai-s. 

 a. Inner portion, 

 a'. Outer portion. 



CiExNus RAFINESQinMA. gkn. nov. 



(See Plate VIII, tigs. 1-11; Plate IXa, figs. 3, 2, 4; anil Plate XVa, figs. 37-39.) 



Page 281. 

 Rafixesquina incrassata, Siifford* (not Hall). 



1. a view of the brachial valve of a lai-ge individual ; showing the area and open delthyrium of the 



pedicle-valve. 

 The intei'ior of the brachial valve ; showing the structure of the aiticnlating apparatus and the 



muscular impressions. 

 A posterior view of the same specimen ; showing the bifui-cate, incisor-shaped (-irdinal process, 



its surface sloping backward to the hinge-line, and partially covered by the deltidium. X 3. 

 A {Cardinal view of a jiortion of the hinge and area; showing the deltidia of both valves, that of 



the pedicle-valve having its .surface distinctly grooved. X 3. 



. The internal cast of a pedicle-valve ; showing the great size of the diductor scar.s, and the tilling 

 of the foi'amen. 



Trenton horizon. Platteville, Wisconsiii. 



Kafinesquina alteunata, Connul. 

 Figs. 6 7. Two views of a specimen presenting normal external characters. 



Fig. 8. An enlargement of a portion of the hinge-ai'ea; showing the deltidia of both valves, and the re- 

 tention of the foramen at maturity. X 3. 

 Fig f<. The interior of a tn-achial valve ; showing the structure of the cardinal process and the adductor 



scars. 

 Fig. 10. The interior of a pedicle-valve ; showing the fiabellate diductor and the narrow adductor scars. 

 Fig. 11. A posterior view of the articulating apparatus of the brachial valve. The incisor-shaped branches 

 of the cardinal process are widely divergent, >and at the bottom of the tiifurcation lies a narrow 

 callosity. The deltidium is well developed but not grooved in the niidiUe, and the dental 

 sockets are deeply marked. X 3. 



Hudson River gi-oup. Cincinnati, Ohio. 

 Foi' other ilhistiations, see Palseontology of Ohio, Vol. I, plate vii, figs. 1-3 ; and Palieontology of 

 New York, Vol. I, plates xxxi and xxxi a. 



Genus LEPT^NA, Dalman. 



Page 276. 



Lept^na tenuistriata Soweiby (= L. rliomhoidulis, Wiitkeii.s). 

 Fig. 12. The interior of a biachial valve. 

 Figs. 13, 14. Views of opposite sides of an individual in which the foramen is retained. 



Hudson River group. Oxford, Ohio. 

 Fig. l."). A jjoition of the hinge of a mature individu.al, enlarged ; showing the foramen situated in front of 

 the area, the slight <levelopment of the deltidium of the pedicle-valve, and the great size of 

 that of the biachial valve, the lattei' being deeply grooved. X 3. 

 Hudson River group. Lehanmi, Ohio. 

 Fig. Itj. An enlarged cardinal view of the central portion of the brachial valve ; showing the deep groove 

 or central depression, the callosity coufoiming to the coutour (pf the cardinal apophyses. 

 Hudson River group. Oxford, Ohio. 



* Since the true generic relations of tlie Chazy species, according to tlic present arrangement, is not fUlIy ascertaiueii, 

 this specific name Is retained fur Die Trcnlon S|iccies. Sliould the original Leptana incrassata, of Che Chazy, prove to be a 

 Kafinesquina, the Trenton form will retain the name of Jt. Minnesotensis, N. U. Winchell. 



