116 



THE GEOLOGIST. 



Fig. 3. Producta numerosa, Sow. Internal cast of the ventral valve, from tlie 

 jMagnesian Limestone of the Carboniferous series of Breedon, 

 Leicestershire. A and C, ocdusor, R, divaricator muscular 

 impressions. L, cones, which denote the deep hollows which 

 existed in the interior of the immensely thickened ventral 

 valve, and which were occupied by the spiral arms. 



4. Aulosteges Wangenheimii, de Verneuil and de 'Keyserling, Sp. From the 



Permian Limestone of jMount Grebeni, in Russia. 



5. „ Wangenheimii. Interior of the dorsal valve (enlarged). J, 



cardinal process. A, occlusor muscular impressions. W, 

 oral processes (?) of Woodward. X, Reniform impressions. 

 I am indebted to General Helmersen for these two beautiful 

 examples. 



6. Strophalosia lamellosa, Geinitz, var. Morrisiana, King. From the Mag- 



nesian Limestone of Tunstall Hill (Durham). H indicates 

 the portion of the beak which adhered to marine bodies. 



7. „ Goldfussii, Munster. A very remarkable interior of a dorsal 



valve, recently discovered by Mr. Kirkby, and forming part 

 of his valuable collection of Permian fossils. The occlusor 

 and reniform impressions prqject to an unusual extent. The 

 sockets for the articulation of the valves are clearly seen on 

 either side of the cardinal process, J. 



8. „ Goldfussii, internal cast of the ventral valve, from the Mag- 



nesian Limestone of Humbleton HiU ; showmg the occlusor 

 and divaricator muscular impressions. 



9. 9^. Chonctes Pratt ii, N. Sp. (0 Nat. size. This beautiful specunen (from 

 the collection of Mr. Pratt) is here given as an illustration of 

 the genus, on account of the admirable preservation of its 

 valves. The specimen is silicified, and the valves can be as 

 easily separated as in those of a recent species. Its locality 

 is unfortunately unknomi. The ventral valve is very deep, 

 with a longitudinal depression along its middle ; the dorsal 

 valve is almost flat, with a small elevation toward^s the fr'ont ; 

 both valves are covered with minute striae. 



A portion of the same, magnified, to show the area of both 



valves ; pseudo-delticUum, and cardinal process. 

 Interior of the ventral valve ; A, occlusor, R, divaricator 

 muscular impressions. The cardinal spines and their tubuli- 

 form orifices are here clearly exhibited. 

 Interior of the dorsal valve ; j, cardinal process ; A, and A', 

 anterior and posterior occlusor muscular impressions ; o, 

 ovarian spaces (.^) ; X, reniform impressions. The gi-anular 

 prominences (described in the text) are here beautifully 

 exhibited. 



13. Strophomena rhomboidalis, Dalman. Showing the position of the occlusor 

 and divaricator muscular impressions, as weU as two cor.ical 

 subspiral prominences, L, which I suppose to have been 

 produced by the mantle pressing upon the spiral ai'ms, ( V) as 

 already described in the same valve of Bavidsonia. Enlarged 

 from a specimen in Queen's College, Galway, and which ^vas 

 originally connnunicated to me by Professor King. 

 14 & 14^ Strophodonta dcmissa, Conrad, Sp. Exterior of both valves ; 



from the Hamilton Group of Western New York, America. 

 Fig. 14 shows that no fissure or pseudo-deltidium interrupted 

 the regularity of the area in either valve ; also the suuill, 

 longitudinal strii^e with which it is covered. 

 dcmissa. Interior of the ventral valve (enlarged), to show the 

 teeth and small testaceous projections between them. A, 

 occlusor, R, di^'aricator muscular impressions. 

 demissa. Interior of the dorsal valve. J, cardinal process. 



10. 

 11. 



12. 



15. 

 16. 



