602 



FOSSIL SHELLS OF THE OLD RED SANDSTONE. 



stratified deposit, which is unconformable to the adjoining masses of Old Red Sandstone. On the 

 other hand, I have recently been informed by Mr. Malcolmson, that Mr. Miller of Cromarty 

 (who has made some highly interesting discoveries near that place), pointed out to him nodules 

 resembling those of Gamrie and containing similar Jishes, in highly inclined strata, which are 

 interpolated in, and completely subordinate to the great mass of Old Red Sandstone of Ross and 

 Cromarty. 



This important observation will I trust be soon communicated to the Geological Society, for it 

 strengthens the inference of M. Agassiz respecting the epoch during which the Cheiracanthus and 

 Cheirolepis lived. In the mean time the phenomena at Gamrie may be explained, by supposing 

 that the beds in which the nodules there occur, are regenerated or made up of the detritus of the 

 adjoining Old Red Sandstone. At all events, certain species of Cheiracanthus and Cheirolepis, 

 as above stated, belong to undisputed strata of the Old Red Sandstone, while no traces of these 

 genera have been perceived in the Carboniferous System. 



These two curious genera have not yet been found in the Old Red Sandstone of England. 



FOSSIL SHELLS IN THE LOWEST BEDS OF THE OLD RED SANDSTONE, PI. 3, 



(See pp.183— 191.) 



The shells are described by Mr. J. de C. Sowerby. Those marked * occur also in the Upper Ludlow 

 Rock and are figured in PI. 5., thus proving a transition from the Old Red into the Silurian System. 



Cypricardia cymbceformis, f. 10 a. (Cardites carpomorphus, Dalm., Act. Holm., 1824, p. 372. 

 t.4. f. 2. Cardium carpomorphum, Hising. Petr. Suec, p. 63. 1. 19. f. 5.) Transversely ob- 

 long, striated near the beaks, valves very deep, carinated ; posterior extremity suddenly con- 

 tracted into a point; beaks small, incurved, close to the anterior extremity; length 5 lines, 

 width 11 lines, depth of each valve 4 lines. 

 Loc. Felindre on the Teme, 10 miles west of Knighton. 



Pullastra IcBvis, f. 1 a. Transversely elongated, slightly convex, smooth, plain; anterior side small, 

 rounded ; front straight, nearly parallel with the hinge line ; posterior side large, rather flat- 

 tened towards the edge, which is nearly straight and oblique ; length f inch, width l£ inch. 

 Loc. Horeb Chapel, in the Cwm-dwr, between Trecastle and Llandovery. 



Cucullcca antiqua, f . 1 b and 12 a. Transversely ovate, rather convex, smooth; posterior side 

 largest, acutely- angular ; internal lamina longitudinal ; length from 3 to 4£ lines, width from 

 4 to 6| lines. 



Loc. Horeb Chapel. Felindre on the Teme, 

 Cuoullcea ovata, f. 12 b. Transversely ovate, convex, even ; beaks near the anterior extremity ; 

 interior lamina longitudinal, not oblique ; length 9 lines, width 13 lines. 

 Loc. Horeb Chapel. 



Cucullma Cawdori, f. 11. Transversely elliptical, convex, posteriorly obliquely truncated; a 

 rounded ridge extends from the nearly central beak to the posterior angle of the margin ; in- 

 ternal laminae oblique; length 4 lines, width 7 lines. 



This shell is named after the Earl of Cawdor who found it. It ought to have been figured 

 among the Upper Silurian fossils. 

 Loc. Freshwater East, Pembrokeshire (see p. 391), 



