VI PREFACE. 



acteristic types from the several geologic formations, and to 

 give at the same time a comprehensive representation of all 

 the classes of animal life. To accomplish this, and place the 

 collection within pecuniary reach of those for whose benefit 

 it was designed, we have made use of plaster copies of the 

 more unique and rare forms, — originals of which it would be 

 impossible in many cases to obtain, and in others too expen- 

 sive. Moreover, for purposes of illustration, a carefully made 

 copy of a perfect specimen is far better than a poor or frag- 

 mentary original. The greater number of forms among the 

 invertebrates and plants we have been able to represent by 

 carefully chosen original specimens, so that the originals in 

 the collection far outnumber the casts in genera and species 

 as well as in individual specimens. 



It is believed that this series meets a felt want, and will 

 prove an invaluable adjunct to lectures and text-books in 

 unfolding the march of life through the successive ages. As 

 has been observed, the series is a compend of Palseontological 

 History, presenting in proper proportions the varied forms 

 which life has assumed from the Archtean Protozoan up to 

 Man. The dullest student can detect in this selection biological 

 order and chronological sequence. It is intended to be a com- 

 ]>Iete cabinet for the Geological Museum of our Colleges. 



The specimens are adapted by their size and form for vari- 

 ous positions in a collection. Most of them are suitable for 

 the shelves of a museum; a few of the casts are large slabs, 

 and intended for a place upon the walls, while a small minor- 

 ity are huge objects calculated to stand on pedestals in the 

 central parts of the room. The display of this large Geolog- 

 ical collection is one of its most noticeable and excellent 

 features. 



A clearly printed label accompanies each specimen, giving 

 ill full the name of the fossil, the author of the species, its 

 geological formation, and the locality where it was found. 



The numbers in brackets are the numbers of casts, as 

 recorded at our Museum, and as published in the old " Cata- 



