26 NOTES ON THE BRITISH JURASSIC BRACHIOPODA. 



is a general tendency among collectors to place in their 

 cabinets only good and well-defined typical specimens, and 

 to reject those which are intermediate in form between two 

 closely allied species. This is a great mistake, as many of 

 these intermediates are very often of greater importance 

 to the brachiopodist than the typical specimens. Neither 

 should we too hastily reject fragmentary shells before care- 

 fully examining them. 



Before concluding these erratic remarks I should like to 

 point out another direction in which original research might 

 be profitably conducted. That is the working out of the 

 " Evolution of the Brachiopoda " — a difficult task it must 

 be admitted, but, nevertheless, a most interestiug one. 

 Much has been done in this direction during the past few 

 years by Messrs. C. E. Beecher, J. M. Clarke, W. H. Dall, 

 J. Hall, and others, of America; P. Fischer, L. Joubin, and 

 P. D. Q^hlert, of France ; and other distinguished savants 

 (10, p. 5). 



Fully alive to the fact that I have not stated one quarter 

 of what might be said respecting this interesting class of 

 molluscs, I am compelled by considerations as to space to 

 abstain from adding any more. We will therefore proceed 

 at once to a consideration of the Jurassic Brachiopoda. 



Under the term Jurassic is included the whole of the 

 strata from the Psiloceras (x4m.) pla^iorhis beds of the Lias, 

 up to and including the Purbeck beds. 



I purpose following Davidson in his division of these 

 rocks as adopted by him in his Monograph, not because 

 it is an altogether perfect classification from a palaeontolo- 

 gical standpoint, but because we shall frequently have to 

 refer to his work, and because it is the one most generally 

 in use at the present time. 



