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PROCEEDINGS OE THE GEOLOGICAL SOCIETY. 



[Mar. 6, 



always more or less fragmentary. The Gasteropoda seem to have 

 suffered no injury prior to inhumation. In several places the spe- 

 cimens, even as casts, are so badly preserved as scarcely to be 

 determinable. This ajjpears to result from two causes, — sometimes 

 being apparently the fault of the investing matrix, whose preservative 

 qualities have been poor ; and at others it is owing to the distortion 

 of the specimens by compression during the process of fossilization. 

 The most remarkable instance of the latter kind that I have met 

 with is near to Hampole Stubbs, where there is a bed of compact 

 brown limestone full of Axini pressed flat, and, in consequence, 

 broken into many pieces. I observed another example of this kind 

 at Conisborough, where Terebratula elongata, which is not a rare 

 shell there, and of rather large size for Yorkshire, is almost invariably 

 more or less distorted by pressure, while the shells of other species — 

 Gasteropods and Conchifers — are scarcely ever similarly affected. In 

 this case the Terebratula} must have been less able to resist the amount 

 of pressure to which the organic remains of this locality were sub- 

 jected than their associates. And perhaps this may be explained, in 

 the first place, by their much thinner shell, and in the second, because 

 of their having been imbedded with closed valves, their dental system 

 not allowing the easy opening or dislocation of the valves after the death 

 of the Mollusk, which would thus prevent the entrance of sediment into 

 the cavity of the shell, to the great disadvantage of the valves resisting 

 the pressure of the gradually increasing superincumbent mass. 



Moorhouse. — One of the most interesting localities is an old quarry 

 near to the hamlet of Moorhouse, where Axinus dubius occurs in 

 great profusion, and most finely developed, both in respect to size, 

 thickness of shell, and general character. Its peculiar umbonal 

 ridges are very finely displayed in the casts of this locality. Several 

 other species likewise occur, and amongst them some of the rarest 

 of the Yorkshire forms. The limestone is oolitic ; and there is one 

 bed in particular which contains the fossils most abundantly ; its 

 position is only seven or eight feet above the Lower Red Sandstone, 

 which is exposed in the same quarry. 



Hampole. — About half a mile to the east of the preceding locality 

 is another old quarry, of very ignoble appearance, at Hampole, where 

 there are some beds of fossiliferous limestone apparently situated a 

 little above the oolitic beds of Moorhouse. From this spot I have 

 obtained seventeen species, and many of them are immature and some- 

 what dwarfed. Axinus dubius, which is so large at Moorhouse, is here 

 never more than half-an-inch in width. And Turbo helicinus, which 



all connexion between the valves ceases, in which state they wonld subsequently 

 be imbedded, were a deposition of sediment to take place before the decay of the 

 valves themselves. It is extremely probable that this is one of the causes of the 

 valves of fossil Conchifera so often occurring detached. When shells of this 

 class are found fossilized with their valves closed and in perfect juxtaposition, it 

 is natural to suppose that their ligament was slight and of little strength, or that 

 they were burrowers. or, at least, if not burrowers, that they had been enveloped 

 in sediment while living; so that, on the relaxation of the adductor muscles from 

 death, the valves woidd be kept closed by the external pressure of the siuTounding 

 secliment. 



