CALCIPEROUS SANDSTONE OF Ell's. 579 



The same Anthracosia is found sparingly in a shale at Billow 

 Ness, though its position (3168 feet) in the series at that place 

 appears to be considerably higher than at Kilrenny Mill. 



Obseevations. 



The thickness of strata in the two sections described, and the dis- 

 tance of the various marine beds from the base of the Carboniferous 

 Limestone, are obtained from a careful and detailed examination of 

 the rocks, bed by bed. Still it should be observed that the amount 

 of strata between the different marine zones must of course be taken 

 as close approximations only ; for most of the beds, particularly 

 the sandstones, are subject to such rapid alterations of thickness 

 that no two sections taken twenty yards apart are ever exactly 

 alike. 



In the group of marine beds at the top of the series that are seen 

 between St. Monans and Pittenweem, the species are all common to 

 the Carboniferous Limestone, with one exception, SanguinoUtes 

 ahdenis. The only difference which they present, when compared 

 with the fauna of the latter rock-group, consists of the comparative 

 abundance of Lamellibranchs, the scarcity of Brachiopods, and the 

 almost entire absence of corals, excepting the highest limestone 

 (zone 1). 



In the Encrinite-bed (zone 5), which is the next marine zone, 

 though separated from those above by nearly 1800 feet of strata, 

 the species with scarcely an exception also all range up into the 

 overlying series. It was this fact that caused Mr. Brown to pro- 

 pose to group the measures from the Encrinite-bed upwards with 

 the Carboniferous Limestone. 



It is not, in fact, until we reach the strata below zone 5 that much 

 difference is to be observed in the character of the marine fauna ; 

 and even then, if we take the list of species merely, more than four 

 fifths of them are found to pass up into the Carboniferous Limestone. 

 But among the few species peculiar to the series are one or two that 

 occur so often and so abundantly as to mark these lower measures 

 with special palgeontological features. These are the prevalence of 

 the Lamellibranchs, Myalina modioliformis and Schizodus JSalteri, 

 the former shell being more especially characteristic, as the preced- 

 ing portion of this paper will have made evident. Among other 

 species characteristic, though in a less d^ree, are Littorina scoto- 

 hurdigalensis, Macrocheilus ? striatulus, and an Orthoceras allied to 

 0. cylindraceum. As a negative character of some value, there 

 is the remarkable paucity of Brachiopods and Corals, which here is 

 more noticeable than in the strata above, the former class numbering 

 only three species {Rliynchonella phurodon, Lingula mytiloides, and 

 L. squamiformis) and the latter two {^Stenopora tumida and Alveo- 

 lites septosus). Altogether 83 species of marine fossils have occurred 

 to me below the Encrinite-bed. Of these, 15 are confined to the 

 Calciferous Sandstones *, as given in the following list : — 



* Not including the species of Anthracosia, Anthracomya, and Carbonia, as 

 well as one or two others of doubtful habits. 



2n2 



