Mr. R. Etheridge, Jun., on Carboniferous Opercula'^ 25 



IV. — Descriptions of certain peculiar Bodies loJiich may he 

 the Opercida of small Gasteropoda^ discovered hy Mr. James 

 Benniein the Carhoniferous Limestone of haw Quarry^ near 

 Dairy ^ Ayrshire^ loith notes on some Silurian Opercida. By 

 11. Etheridge, Jun. 



[Plate II.] 



Introduction. — The object of the present communication is 

 to briefly describe several small bodies which Mr. Bennie and 

 myself are mutually agreed in regarding as the opercula of 

 minute Gasteropoda, and which were discovered by the former 

 some time ago in a bed of highly fossiliferous and siliceous 

 limestone near Dairy. The interest attached to these remains 

 lies in the fact that occasionally small entire shells are found 

 in the same stratum with one form of the opercula about to be 

 described in situ, thus affording a very good demonstration of 

 their true atiinity. The description of a large Naticopsis with 

 the operculum in situ and several examples of Euomplialus 

 sculptus from the Wenlock Limestone, all contained in the 

 British- Museum collection, will complete the account. 

 Mr. Bennie has kindly furnished me with the following notes 

 on the bed of limestone from which the fossils were obtained. 



Law Quarry is situated on the Cubeside farm, about two 

 miles north-west of Dairy, and only a few hundred feet from 

 the edge of the great mass of bedded traps which stretch from 

 Dairy to Largs. The band of limestone forms a subsidiary 

 bed (probably the lowest) in the Howrat Limestone ( = the 

 Hurlet or Main Limestone), the lowest bed of the Lower Car- 

 boniferous Limestone group of Scotland. It may be 12 feet 

 or so in thickness, and is very hard and compact where solid 

 and unweathered. The bed is highly charged with siliceous 

 matter, as a large percentage of the contained fossils have been 

 changed into some form of silica. A bed of Lithostrotion is 

 present, every polypite of which is completely silicified. The 

 percentage of silica is so high that the limestone is only 

 wrought for manure by the neighbouring agriculturists. 



The fossils are obtained by washing the disintegrated 

 material found on ledges of the quarry-face and in fissures and 

 pockets made by the natural jointing of the rock. 



Interest will be added to the matter if the descriptions are 

 prefaced by a brief epitome of the structure of the Gasteropod 

 operculum, and a similar account of the number of genera in 

 which this organ has been found in position in Palaeozoic shells, 

 a by no means frequent occurrence. 



The operculum of the Gasteropoda consists of a layer more or 



