428 Two hitherto undescribed Species of lladidria. 



following appear the most important : — Belemmtes conicus, 

 B. compressus, Pecten aequivalvis, P. sublaeMs, Avieula 

 inaequivalvis, A. cygnipes, Plicatula spinosa, O'streae. These 

 fossils I have found most abundant below the signal cliff at 

 Staithes, where the shales are better exposed than elsewhere. 



At the same place, but nearer low water mark, probably 

 10 ft. or 12 ft. lower in the series, one of the irony seams is 

 very full of fossils, containing Ammonites Cleveland's, A. 

 Stokes/7, Turbo undulatus, Cardium multicostatum, Isocardia 

 lineata, Corbula cardioides, My a, b. scripta, M. literata, Am- 

 phidesma recurvum, Terebratula subrotunda, T. tetraedra, 

 T. triplicata, T. bidens. 



Still nearer the landing-place at Staithes, another layer of 

 ironstone makes its appearance on the Scar, equally prolific 

 in fossils, of which the chief are, Isocardia lineata and Am- 

 monite maculatus. The latter are rather remarkable, from 

 their being filled with solid crystals of carbonate of lime, 

 which often render the whorls, especially the inner ones, semi- 

 transparent. 



Below these layers of ironstone, the seams of sandstone are 

 filled with fossils in the greatest confusion. Ophiura Miller/, 

 O. sp. ; Cidaris, an undescribed species ( Woodward) ; Denta-. 

 Hum giganteum, Belemmtes elongatus, Modiola scalprum, 

 M. HiUdna, Avieula inaequivalvis, Pecten sublaeVis, Plagios- 

 toma laeviuseulum, Gryphae'a bullata?, O'streae. The two 

 Ophiurae, Cidaris, Modiola scalprum, and Plagiostoma 

 laeviusculum, are rare, the remainder very abundant, forming 

 a rich harvest for the industrious collector between Staithes 

 and Saltburn, where blocks of the sandstone have fallen from 

 the cliffs above upon the shore. 



( In one of the sandy seams near the base of this stratum 

 was found the ^/sterias described above : near the same part, 

 Pholadomya Murchisom is found with several bivalvular 

 shells, often imperfect. 



Occasionally hard seams of ironshot sandstone are met 

 with, filled with Cardium truncatum, which is very abundant 

 between Staithes and Saltburn. It is rather remarkable, that 

 the broken, or separated, valves are generally found distinct 

 from the double, or perfect, specimens ; as if the former had 

 consisted entirely of dead shells, with the ligament become 

 destroyed. 



It was in 1833 that I was first struck with the extreme 

 regularity in the distributions of fossils in the lias group of 

 Yorkshire. This immediately led me to imagine that Dr. W. 

 Smith's theory of identification might be carried even to a 

 still more extended degree of application than had hitherto 



