DAVIDSON — SCOTTISH CARBONIFEROUS BRACHIOPODA. 



237 



smaller,* but not tlie less interesting on that account, and are in 

 many instances far more perfectly preserved than any similar species 

 hitherto noticed from other countries, so that we have been enabled 

 in several instances to complete the descriptions of the characters 

 both internal and external, which were but imperfectly made out in 

 our larger work. In a very interesting paper by Mr. McAndrew^ on 

 the comparative size of marine mollusca, it is clearly proved that 

 "although the size attained by mollusca may be influenced by various 

 conditions in different localities, as a general rule each species attains 

 its greatest size, as well as its greatest number in the latitude best 

 suited to its development." Much has, however, to be learned 

 relative to the habitats and distribution of the British Carboniferous 

 species, and correct lists of those peculiar to each horizon, zone, or 

 stage, have still to be drawn up, as well as those that partake of 

 a larger or more restricted vertical range ; and indeed, when prepar- 

 ing my monogTaph for the Paleeonto graphical Society, I found that 

 the information I could obtain upon this very important subject was 

 so scanty, and often so unsatisfactory and contradictory, that I was 

 obliged to confine myself almost entirely to the working out of the 

 species, which had themselves been thrown into much confusion, on 

 account of the multitude of erroneous identifications or mis-naming 

 prevalent in almost every British pubhc and private collection, while 

 the nomenclature was likewise most heavily burdened vnth a vast 

 number of synonomous and useless denominations. It could not, 

 therefore, be expected in most instances that local enquirers could 

 famish that correct information relative to the distribution of the 

 species in their particular districts until they had become familiar 

 with the characters of the species themselves ; it would have to a 

 certain extent been just as if we were to expect that a person could 

 read fluently who was but very imperfectly acquainted with the 

 name and shape of his letters ; but it is to be hoped that before long- 

 that important information '^dll be forthcoming, and which no one 

 could furnish or work out so well as those who reside in the localities 

 where the fossils are found. The dif&culty and perplexity I so often 

 experience in the identification of specimens and species should deter 

 many who may be even less experienced than myself from too hastily 

 supposing that a shell which may not be familiar to their eye is 

 really new ; for in order to ascertain whether a species is in reality 

 so, a very considerable amount of research is required, a research 

 many cannot undertake, from the want of books or means of com- 

 parison. I would, therefore, urgently impress upon the minds of 

 young paleeontologists the very great importance of caution, and not 

 too hastily or highly consider as new what they might not be 

 acquainted with, otherwise the science will become so burdened with 

 synonpns and useless denominations that it will deter many from 



* Conditions arising from food and climate no doubt modify form and size, and 

 modifications of form not amounting to malformation might arise from diseased 

 condition. 



