X 
PREFACE. 
to indicate a considerable number of new generic forms, which it is believed are 
well founded in nature, and which will prove useful in the study of this class 
of fossils. The total number of genera described in the volume is sixty-five, 
of which twenty-six are new to science. Thirteen of these belong to the 
Monomyaria and thirteen to the Dimyaria. 
The total number of species described is five hundred and twenty (520), of 
which two hundred and thirty-eight (238) belong to the division Monomyaria, 
and two hundred and eiglity-two (282) to the Dimyaria. Four hundred and 
eighty-five (485) of these species belong to the Devonian System, as at present 
recognized. Thirty-five are from the Waverly or Lower Carboniferous, and 
five Silurian species are introduced for the purpose of comparison. The 
former volumes of the Palaeontology contain altogether descriptions and illus¬ 
trations of about twenty genera and one hundred species of Lamellibranchiata. 
In the revision of the species, and the publication of this volume, the author 
acknowledges with great satisfaction the assistance rendered by Mr. C. E. 
Beecher. The original drawings of the fossils have been chiefly made by 
Mr. George B. Simpson. About twelve plates are by Mr. Emerton, and four 
by Mr. J. W. Hall; the supervision of the drawing and lithography was in 
charge of Mr. It. P. Whitfield. The six plates of recent additions have been 
drawn by Mr. E. Emmons. The lithography has been done chiefly by Mr. 
Philip Ast and Mr. Paul Riemann. 
The author has been indebted for the use of specimens for illustration in 
this volume to the late Dr. James Knapp, of Louisville, Kentucky; to Prof. 
J. S. Newberry and Prof. J. J. Stevenson, of New York; to Mr. C. E. Beecher, 
of Albany, and for the loan of specimens from the collections of the Cornell 
University. Prof. Winchell, of Ann Arbor, has kindly loaned the types of all 
his described species from the Marshall Group and Burlington sandstones, of 
which farther use would have been made in comparisons with New York 
forms, but for the fact that he intends soon to publish the descriptions of the 
same with full illustrations of the species. 
Albany, November, 1885. 
