10 CARBONICOLA, ANTHRACOMYA, AND NAIADITES. 



and their very varying forms, I have come to the conclusion that either they were 

 capable of inhabiting both lakes and estuaries on the one hand, and the open sea 

 on the other, or else the marine and fresh water forms are so similar in appearance 

 that they can only be identified by reference to those which may occur along with 

 them in the bed. Thus when, (as in Coalbrookdale and Lancashire), [I doubt the 

 latter locality 1 ] we find them associated with undoubted marine forms, we can 

 only conclude that they themselves were inhabitants of the sea; but if they 

 happen to occur unaccompanied by such well-recognised forms, then we may 

 assume that they represent lacustrine or estuarine conditions, the probability 

 being that had the strata been formed under the sea marine shells would have 

 been preserved along with those of this genus." I have shown above that the 

 mixture of marine forms with Garbonicola (Anthracosia) is by no means so 

 common as might be supposed from this remark, and that it may be accounted 

 for in other ways than those advanced by the Professor ; and I am sure that the 

 true reason of this group of shells being a " bane to paleontologists " is because 

 they have never been systematically collected and studied. It is perfectly 

 astonishing to see the paucity of specimens of these shells in museums, and more 

 so in the museums of large towns situated in coal-measure districts. It is, 

 indeed, a matter of very considerable difficulty to obtain these fossils in situ, and 

 unless the greatest care is observed, and the collector possesses an intimate 

 acquaintance with the naked-eye characters of the various shells and rocks on the 

 waste-heaps, it is very easy to infer that fossils which lie close together on the 

 mound, belonging to widely separated beds, are from the same horizon. Another 

 obstacle arises from the carelessness of many collectors in not labelling each 

 specimen immediately it has been brought home, and often putting them by with 

 others, so that shells from various beds become mixed and the horizons forgotten. 

 I can testify myself to the frequent difficulty and almost impossibility of arriving 

 at any but the approximate horizon of many specimens ; often I have found some 

 of my best specimens lying weathered-out on the rubbish-heap of a pit-bank years 

 after the pit has ceased working, and which, from the hardness of the matrix and 



1 On the authority of Prof. Phillips (article on " Geology," ' Encyclopaedia Metropolitana,' 

 1834, p. 590), who, in speaking of the marine shells in the Lower Coal-measures of Lancashire and 

 Yorkshire, says, " In the midst of this series of G-annister Coal two layers of these shells [Unio] 

 occur, one of them about the middle of the series, considerably above the Pecten Coal, and the other 

 uear the bottom, considerably below that coal." This extract is quoted by Binney in two papers on 

 " The Marine Shells of the Lower Coal-measures " (' Manchester Geol. Soc. Trans.,' vol. i, p. 82, 

 1841; vol. ii, p. 75, 1860). Mr. Bolton, assistant keeper of Owens College Museum, writes me: — 

 " In the Rossendale area of the lower coal-measures a very persistent bed of ironstone shale with 

 ironstone, the whole charged with Carbonicola in the state of casts, occurs immediately over the 

 Bassey or Salts Mine. The same bed has been found at Helpit Edge, Saddleworth. I am sure that 

 careful search would prove its existence in the Haslingden district." 



