PLATE VIII. 



(Figures 1-18, .!'2-31 by R. P. Whitfield; 20, 21 by F. J. Swinton; 19 by G. B. Simpson.) 



Legemi. D. Delticiimii, iieilicle-valve. b. Dental sockets. 



C. Delti<liiim, l)r:u'hial v.alve. t. Teeth. 



A. Delthyriuni. j. Cardinal process. 



K. Foramen. a. Adductor scars. 



F'. Groove on deliliyriiim. I)r;ichial valve. r. Anterior diductor scars. 



A. Cardinal area ; v'. Posterior diductor scars. 

 a. Inner jiortion. 

 a'. Outer portion. 



Genus RAFINESQUINA, gkn. nov. 



(See Plate VIII, figs. 1-11 ; Plate IXa, figs. ], 2. 4 ; and Plate XVa, tigs. 37-89.) 



Page 281. 



Rafinesquina incrassata, Saflbid* (not Iliill). 



Fig. 1. A view of the brachial valve of a large iridividual ; showing the area and open delthyrinm of the 

 pedicle-valve. 



Fig. 2. The interior of the bi-achial valve ; showing the sti-ucture of the articulating apparatus and the 



muscular impi'essions. 

 Fig. 3. A postei-ior view of the same specimen ; showing tlie bifurcate, incisor-sliapeil cardinal process, 



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

 Fig. 4. A cardinal view of a portion of the hinge and area ; showing the deltidia of both valves, that of 



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

 Fig. .'). The internal cast of a pedicle-valve ; showing the great size of the diductor scars, and the filling 



of the foramen. 



Trenton horizon. Platttrdle, Wiscov^nn. 



Rafinesquina altehna'I'a, Convad. 



Figs. 6, 7. Two views of a .specimen i)resenting normal extei'ual ehai'acters. 



Fig. 8. An enlargement of a jiortion of the hinge-area; showing the deltidia of both valves, and the re- 

 tention of the foramen at matui-ity. X 3. 



Fig 'i*. The interior of a brachial valve ; showing the structure of the cardinal process and the adductor 

 scars. 



Fig. 10. The interior of a pedicle-valve; showing the flabellate 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 jii'ocess are widely di\-ei-gent, and at the bottom of the bifurcation lies a nai'row 

 callo.sity. The deltidium is well developed but not gi-ooved in the middle, and the dental 

 sockets are deeply marked. X 3. 



Hudson River gi-oup. Cincinnati, Ohio. 



For other illustrations, see Palasontology of Ohio, Vol. I, plate vii. figs. 1-3 ; and Palaeontology of 

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



Genus LEPT^NA, Dalman. 



Page 27(). 



Lei't^.xa tenuistriata S()woil)y (= L. rlioinJtoidalis, VVilckeiis). 



Fig. 12. The interitu' of a brachial valve. 



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



Huilson River group. Oxford, Ohio. 

 Fig. 1.5. A portion of the hinge of a mature individual, enlarged ; showing the foramen situated in front of 

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

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

 Hudson River gi'oup. Lehannv, Ohio. 

 Fig. 16. An enlarged cardinal view of the central portion of the brachial valve; showing the deep gi-oove 

 oi- central depression, the callosity conforming to the contour of the cai-diual apophyses. 

 Hudson River gi-oup. Oxford, Ohio. 



• Since the true generic relations of the Chazy species, acoorflin(; lo tlie present arrangement, is not fully ascertaiueil, 

 this Bpeciitc name is retained fur the Trenton species. Should the original Leptceita incrassata, of the Chazy, prove to be a 

 Rafinesquina, the Trenton form will retain the name of K. Minnesotensis, N. H. Winchell. 



