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 Croniatites. 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 
Palzxoniscus. 
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 H, 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, pl. u, 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, &e., 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), &¢., never occur. 
