A MONOGRAPH 



-0 



OF 



BRITISH TRILOBITES. 



A Monograph of the British species of the Trilobite group has long been desirable, 

 and would, in accordance with the wish of many friends, have been prepared by me 

 before now, had public engagements permitted it. 



The materials for such a work have hitherto been much scattered ; nevertheless, of 

 late years, they have become very numerous, whilst the publication of such sterling works 

 as those of Barrande, Burmeister, Beyrich, and Loven, have disposed naturalists, as 

 well as geologists and collectors, to pay increased attention to the group, 



I think that a true and natural arrangement of the Trilobites is yet to be given ; and 

 therefore prefer at present to publish the materials in hand, that in the mean time 

 systematic zoologists may have the means of forming their judgment. The group is a very 

 complete one, and no artificial scheme is admissible for its classification. Dr. Emmerich's 

 Essay, of 1845, seems to me to be the nearest approach to a natural grouping of the 

 families ; and I shall follow it meanwhile, in figuring the species, 1 with such additions as 

 are proposed on the next page. The dichotomous arrangement here given is proposed 

 merely as temporary ; but I believe it to be, in the main, a natural one. 



And I trust that, by the time we have arrived at the conclusion of the work, some new 

 and clearer light may be thrown on the affinities and arrangement of this order of 

 Crustacea, as unique in character as it is well defined in geological place. 



1 Our friends will much oblige by forwarding us their best specimens, including any illustrative 

 fragments, in the order of the families as given on page 2. In that way all the materials for a genus will 

 be under the eye together, and no long detention of the specimens need take place. They may be sent to 

 my care, at Mr. Sowerby's Natural History Offices, 45, Great Russell Street, London. 



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