PREFACB. 



while the Genus Stricklandinia is retained for certain forms. It is also 

 proposed to distinguish these allied genera, together with Camabopuoria, as 

 a family Pentamerid^. 



The Genus Crtttonella has been sustained by the character of its in- 

 ternal loop ; while the strophomenoid form, Tropidoleptus, is found to be 

 more nearly allied with the Terebratulidoe than with any other family of 

 the Brachiopoda. 



Of the genera described or discussed under the several families, nearly 

 one-half are those which have been proposed from the study of American 

 species of Brachiopoda, and it is believed that they are well-founded in the 

 characters of the typical species. In some of the genera here named, much 

 yet remains to be done in the study of their internal structure, before we 

 shall be prepared to assert positively their entire characters and relations. 



The printing of this volume was begun in 1862 ; but delays beyond the 

 control of the Author have prevented its appearance until now. The 

 plates of the volume are still unfinished at this date, and some considerable 

 time will elapse before their completion. It is hoped that these illustrations 

 may prove acceptable to the student in Palaeontology. With the exception 

 of a few plates, the lithography has been executed by Mr. F. J. Swinton, 

 whose ability and long experience have enabled him to present the work 

 in a very superior manner. The drawings have been made with great care 

 and fidelity by Mr. R. P. Whitfield, who has excelled both in the accurate 

 delineation of the character and markings of the species, and also in the 

 preparation of specimens to illustrate the internal structure. 



I am greatly indebted to Mr. John Paterson, for his careful supervision 

 of the volume as it has been passing through the press, and more especially 

 for his kind attention to this matter during some periods of my personal 

 absence. 



My acknowledgements are due to many gentlemen for the use of 

 specimens given or loaned to me for study, while the work has been in 

 progress, and of some of these, mention has been made in the body of 

 the work. It is especially gratifying to me to acknowledge the liberality 



