ON MINERAL VEINS IN CARBONIFEROUS LIMESTONE. 369 



Valvata anomala, Moore. Kirkbya plicata, Jones Sf Kirkby. 



pygnifea, Moore. Moorea tenuis, Jones, MS. 



Vertigo Murchisoniae, Moore. Terebratula hastata, Sow. 



Bairdia plebeia, lieuss. Orthis Michelini, Kon. 



bievis, Jones <!>■ Kirkby. Atrypa, sp. 



Cythere bilobata, Mi'inst. Spirorbis. 



fabiilina, Jones Sf Kirkby. Serpulae. 



intermedia, Miinst. Encrinites. 



anibigua, Jones, MS. Bryozoa, various species. 



tequalis, Jones, MS. Corals, several species. 



spinifera, Jones, MS. Ecbinodermata. 



Thraso, Jones, MS. Couodonts. 



Considerable palseontological interest attaches to the presence, under these 

 peculiar conditions, of such genera as Helix, Proserpina, and Vertigo, as, 

 with one exception, they are the earliest recognized land shells, and also to 

 Valvata, Hydrobia, and Planorhis, the oldest freshwater genera yet known. 

 In the paper above mentioned, I referred to the difficulty that exists in 

 always assigning the shells of different ages, when thus mixed together, to their 

 true geological horizons. Although in general this difliculty does not occur, 

 it may happen with those which are new, or have not been previously stra- 

 tigraphically recognized. 



It was not unnatural that I should have supposed these land and fresh- 

 water shells, when accompanied by a large Liassic fauna, to be of the same 

 age ; but with regard to the Valvata anomala, the V. pygmaa, and the 

 Planorhis Mendipensis, the evidence I have since obtained of the presence of 

 these shells in the mining- districts of the North, leads me to the conclusion 

 that it is probable that these land and freshwater species are rather to be 

 assigned to the earlier period of the Carboniferous Limestone, a fact that 

 will still enhance their palfeontological interest. The presence also of other 

 freshwater genera, to be hereafter noticed, occurring in considerable num- 

 bers in the veins, induces me to think that there are some freshwater beds 

 connected with the Carboniferous Limestone from whence they may have 

 been derived which have yet to be discovered ; and I hope my geological 

 friends who are working in Carboniferous-limestone districts will turn their 

 attention to this point ; for of all formations, less, I believe, is really known 

 or realized of the great physical, palseontological, and other changes which 

 have occurred during the Carboniferous period than of most other geological 

 deposits, and there yet remains a great work for some geologists to take up in 

 this direction. 



In other mining-districts organic remains are generally less plentiful 

 than in the Mendip area ; but I have not failed to detect them, more or less 

 abundantly, except in one instance, in that of the Cononley Mine in the 

 Airdale district. It often happens that, though they are wanting in some 

 samples of the " dowks," they may still be obtained from otliers at higher or 

 lower levels in the same mine. Although they have in all instances been 

 selected promiscuously for examination, fossils have been found in more 

 than one half of the samples. 



The following lists of " dowks," with notes of their organic contents, are 

 selected to show the general character of the vein-stuff after it has been 

 prepared by washing. 



Keld-Head Mines, Wensleydale. 



48 ft. from surface. A very mineralized, brownish, or drab marl ; when 

 washed chiefly a residuum of quartz grains. Organisms rare, consisting 

 of Encrinites, Serpulce-liJce tubes, Involutina, 



