THE BRITISH FOSSIL BRACHIOPODA. 381 



approximate numerical comparison of the genera and species that have existed 

 during the various more or less extended geological periods ; and many years will, I 

 fear, have to pass away before some master mind will be able to grapple with the both 

 scattered and accumulated observations of two and a half centuries, and reduce the 

 number of genera and species within reasonable limits, so that something like trust- 

 worthy data may be adduced. Much of the confusion that at present prevails 

 must be attributed to the still imperfect information on zoology and comparative 

 anatomy among a large proportion of those who describe species, and who often, 

 without having ascertained whether their so-termed species has not already been 

 discovered and described, find it more convenient to give it a new name, and, to make 

 matters worse, neglect in many cases to give a figure or illustration in support of 

 their views. No new species should be admitted that is not accompanied by a figure ; 

 and this view has been recently advocated in a very decided manner by the International 

 Congress held at Paris and at Bologna, and should pass as law. 



But to return to our subject. I cannot do better than extract from Lyell 1 the 

 following passage : " Nothing is more remarkable in ... . the Silurian strata generally 

 of all countries, than the preponderance of Brachiopoda over other forms of Mollusca. 

 Their proportional numbers can by no means be explained by supposing them to have 

 inhabited seas of great depth, for the contrast between the Palaeozoic and the present 

 state of things has not been essentially altered by the late discoveries made in our deep- 

 sea-dredgings. We find the living Brachiopoda so rare as to form about one forty- 

 fourth of the whole bivalve fauna ; whereas in the Lower-Silurian Rocks, .... where 

 the Brachiopoda reach their maximum, they are represented by more than twice as 

 many species as the Lamellibranchiate Bivalves. There may, indeed, be said to be a 

 continued decrease of the proportional number of this lower tribe of Mollusca as we 

 proceed from older to newer rocks." 



As already remarked, it is not possible, in the present state of our knowledge, to 

 pretend to be able to arrive at anything definite or satisfactory with respect to the 

 number of good species that have been discovered, as a very large proportion are in 

 reality simply modifications in shape, and consequently synonyms. This lamentable 

 confusion has also arisen in a great measure from the uncertainty which prevails 

 in the Palaeontologist's mind as to what should constitute a species, and where 

 to draw a line between forms so nearly related that they seem to pass one into the 

 other by insensible gradation. Nearly 300 genera or generic names have been 

 proposed, and of these some 139 have been provisionally retained and recorded in 

 my Tables. The genera, however, are not so numerous that they cannot be investigated 

 and critically compared. To reduce the number of useless and confusing names must 

 be the aim of future palaeontologists. Then, again, the very great abuse of the name 

 variety has in no small degree added to the confusion we have been gradually drifting 

 1 ' Students' Elements, &c.,' 1874, p. 468. 



