6 CARBONICOLA, ANTHRACOMYA, AND NAIADITES. 



marine remains do not prove as many relative changes of land and sea, but that 

 the Coal-measures were deposited in an estuary, into which flowed a considerable 

 river, subject to occasional freshes ; and he conceives that this position is 

 supported by the fact of frequent alternations of coarse sandstones and conglo- 

 merates with beds of clay or shale containing the remains of the plants which 

 have been brought down by the river." 



A very important statement is made by the officers of the Geological Survey 

 in the large memoir ' The Geology of the Yorkshire Coal-field,' p. 14 : — " The few 

 mollusca met with may be divided into two groups. One group contains shells, 

 such as Anthracosia and Anthracomya, which are allied to recent fresh- water forms ; 

 the other group consists exclusively of marine genera, such as Aviculopecten, 

 Posidonomya, and Goniatites. These two groups have never yet been found 

 together, and the marine forms occur only on a few horizons and in beds of no 

 great thickness ;" though this evidence is rather discounted by the notice (at 

 p. 85) of a section at Hoarstones Road showing black shale with Anthracosia 

 acuta, A. robusta, var. B, Aviculopecten papyraceus, Goniatites, and scales of 

 Palseoniscus. 



The absence of Carbonicola (Anthracosia) and its allied forms from the 

 Gannister-beds of Lancashire and Yorkshire, stage E of Professor Hull, and, 

 indeed, with one or two exceptions, from the whole of stage B, is very marked ; 

 and I have reason to believe that he may have been misinformed by local collectors 

 as to the true genera of the specimens : many shells which have been shown to 

 me from these beds as Carbonicola and Naiadites I have found to be crushed 

 specimens of Schizodus. This was the case with a shell figured by Mr. George 

 Wild ('Trans. Manch. Geol. Soc.,' pt. 13, vol. xxi, pi. ii, fig. 7). I have been 

 permitted to examine this specimen, and have no doubt as to its being Schizodus 

 Salteri ; and as the same shell occurs in the North Staffordshire Gannister-beds, 

 I think it exceedingly probable that either this shell or perhaps a true Modiola, 

 which is found in the Wetley Moor ironstones, has been mistaken for Naiadites. 

 Strange to say, Prof. Hull has made no mention of Anthracosia, &c, occurring in 

 the Penneystone of Coalbrookdale (stage E) ; while, as to the occurrence of 

 Anthracomya in this stage in Glamorganshire, as quoted by him, this horizon is 

 not given by Salter (' Iron Ores of Great Britain,' pt. 3, 1861). 



It is important to note that in the thin marine bands of the Upper and Middle 

 Coal-measures, with a characteristic marine fauna, differing much from that of the 

 Gannister, especially in the paucity of Lamellibranchiata, Carbonicola (Anthra- 

 cosia), &c, never occur. 



