CARBONIFEROUS CORALS AND BRACHIOPODS 93 
becomes, in itself, a new type to which other specimens 
can be referred. 
There is, however, a very strong objection to the registra- 
tion of a long series of mutations under one and the same 
name. Specimens from different localities, or from the 
same locality but from different horizons, are found to agree 
with certain different figures classed together under a 
single specific name of great inclusion ; they are then cited 
in lists under this specific name, with the result that the 
conclusion is often drawn that the two forms are absolutely 
identical, though they may be, in reality, conspicuously 
different. Mere lists of Carboniferous Limestone fossils, 
including such specific names as Productus giganteus, 
Spirifer trigonalis, Clionetes papilionacea, Clisiophyllum 
turhinatum, etc., etc., convey far less precise information 
than a list of genera in Jurassic Geology. So long as we 
are content to consider every large, longitudinally-ribbed 
Productus as Productus giganteus, every Terebratula or 
Terebratuloid Athyris as Terebratula hastata, and every 
narrow Siphondendroid Lithostrotion as Lithostrotion 
irregulare, and to register them under these names without 
any further information, the palaeontology of the Carbon- 
iferous Limestone could almost be done by occasional 
glances at a section from an express train. 
The information thus conveyed is not only valueless in 
itself, but it tends to retard Carboniferous research by 
making it appear that, in this alone of all the systems, the 
same form may occur at very different horizons and yet 
retain identically the same characters. 
I have made the above remarks as an excuse, if any such 
is needed, for the detailed nature of the descriptions which 
follow. 
In the case of the Brachiopods I have in nearly- all cases, 
referred to the figure in Davidson’s Monograph, which 
most nearly corresponds to the specimen I am describing, 
