PLATE VII— Continued. 



Genus HEMIPRONITES, Pandek. 



Page 238. 



Hemipronite.s, .sp. ? 



Fi^. '20. A view of the i)e(iicle-valve, the cardinal area beiiifj in the plane of vision. The area of the o|)- 



posite valve and the deltidia of both valve.s are shown. X 2. 

 FifT. 21. A cardinal view of the same .sjiecinien ; showing' the characteristic contour upon which is liased 



the sepai-alion of these forms from Clitambonites. X 2. 



Fiff. 22. A sjiecimen cut horizontally across the unibonal region of the j)edicle-valve ; showing the united 

 dental lamellse supported by a median septum. X 2. 

 Lower Silurian. Mujfsia. 



Gends clitambonites, Pander 



Page 233. 



Clitambonites adscendens, Pander. 



Fig. 2cf. A cardinal view, giving the subpyramidal contour characterizing this genus; showing also the 

 foramen in the deltidium. X 2. 



Fig. 24. A pedicle-valve with the apex cut away; showing the peculiar internal sti'ucture of this valve. X 2. 

 Lower Silui'ian. liiissia. 



For fni'ther ilhisti'ation, see Pander, Beitrage zur Geogn. russ. Reiches, j)lates xvii, xviii, and de 

 Verneuil, Geologie de la Russie et des Mont, de I'Oural, plate xii, tig. 3. 



Clitambonites (Outhisina) anomala, Schlotheiiii. 



Fig. 25. A view of the pedicle-valve ; showing the great retrorsion of tlie apex, the liigh cardinal area of 

 the pedicle-valve, and the perfoi-ated <;eltidium ; and also the ai-ea and deltidium of the oppo- 

 site valve. (After de Verneuil, Geol. Russ. et des Mont, de I'Oural, plate xii, tig. 2b.} 



Fig. 26. The interior of the brachial valve ; showing the extreme development of the cardinal ai'ea and 

 deltidium, the latter entirely obscuring the cardinal process; the character of the muscular 

 and vascular scar.« is also distinctly seen. (After Davidson.) 



Fig. 27. The interior of a pedicle-valve. (After Davidson.) 



For further illusti-ation, see de Verneoil, Geol. Russ. et des Mont, de I'Oui'al, plate xii, tig. 2. 



Clitambonites plana, Paiidei-. 



Fig. 28. The interior of the pedicle-valve ; showing the radiating ridges beneath the spondylium. (After 

 Davidson, Introd. Foss. Brach., plate viii, fig. 158.) 



Genus SCENIDIUM, Hall. 



(See Plate VIL\.) 

 P.igeiU, 



Scenidium pyramidale, Hall. 



(See Plate VIlA, figs. 29, 30.) 

 Fig. 29. View of the type-.specimeu ; showing the open delthyrium in each v'alve. X 2. 

 Fig. 30. A cardinal view; showing the size of the areas of the two valves and character of the delthvi-ium. 

 X2. •* 



Niagara group. Liickport, N. Y. 



Scenidium insiune, Hail. 



Fig. 31. A view of the brachial valve ; showing the concave plate (d) in the delthyrium of the pedicle- 

 valve. X 8. 



Fig. 32. The ojiposite side of the same specimen, pedicle-valve. X S. 



Fig. 33. A cardinal view of conjoined valves ; showing the concave plate in the delthyrium (d), the hinge- 

 pl.ate (a) and the medi.in septum (s). X 8. 



Fig. 34. The intiuior of the brachial valve ; showing the elevated hinge-plate and the pi-ominent median 



.septum. X 8. 

 Fig. 35. The interior of a pedicle-valve with an open delthyrium. X 8. 

 Lower Helderberg group. Near Clarksville, N. Y. 



