246 TRANSACTIONS OF THE [.MAR. 15, 



Mollusca usually occur in bands or layers in the shale, and are 

 best preserved in the irregularly-shaped ironstone nodules. An- 

 thracosia robusta occurs in such profusion in certain of the 

 shales as to form thin limestone known as " mussel bands." 



Nearly all the sandstones are marked by worm-burrows and 

 tracks, but no specific determination of these is possible. 



The few species ot Brachiopoda which occur are to be re- 

 garded rather as persistent examples of the older Carboniferous 

 limestone fauna than as true Coal Measure forms. 



Arthropoda are rare, and few of the species are represented 

 by more than half a dozen individuals. 



The Pelecypoda are beginning to receive attention, and it is 

 quite possible that the number of species may be doubled within 

 the next few years. 



Our knowledge of the Gasteropoda is in a lamentable condi- 

 tion, those having been described and figured in such a fashion 

 fifty years ago that few forms can be determined with certainty, 

 whilst the diflflculty of knowing what was meant by some of the 

 old workers acts as a deterrent to those who now wish to take 

 up the study. 



The Cephalopoda have suffered in much the same way, but the 

 admirable catalogues of the British Museum by Messrs. Crick 

 and Foord are clearing the ground, and making known a number 

 of new species. At least half a dozen new forms will need to 

 be added to those here recorded when Volume III of the Cepha- 

 lopoda Catalogue is published. 



Fishes, the dominant forms of life, existed in great numbers, 

 certain species having also a great range in point of time. At 

 least thirty-nine species are known, and there is good reason to 

 believe that the number will be considerably increased as the 

 result of researches 1 am now carrying on. It is interesting to 

 note that within the last year and a-half I have found two ex- 

 amples of Listracanthus,a. genus not hitherto known in England, 

 but characteristic of the American Carboniferous. Amphibia 

 are exceedingly rare ; only three specimens are known. 



As to what were marine forms, what brackish and what fresh- 

 water, I do not care to discuss at present. My own observations 

 have led me to believe that no hard and fast rule of what forms 

 are truly marine, etc., can be yet drawn. The question of asso- 

 ciation of species has not been fully considered, nor is it at all 

 certain that many species were restricted to one habitat. 



My conclusions at present are that man}' forms supposed to 

 be brackish water and others supposed to be marine forms are 

 identical and could live under either conditions, whilst not a 

 few of the fishes could penetrate to great distances along water- 



