PREFACE. 
while the Genus Stricklandinia is retained for certain forms. It is also 
proposed to distinguish these allied genera, together with Oamarophoria, as 
a family Pentameridas. 
The Genus Cryptonella 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 Terebratulidse 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. P. 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. B. 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 
