192 BULLETIN OF THE 
there were taken over 3,500 entire Trilobites; 2,200 were in a 
condition to warrant sections being made of them. Comparatively 
few had the appendages well preserved, and now there are but 270 
sections,* affording more or less satisfactory evidence of their pres- 
ervation. It was very difficult, after obtaining the material, to cut a 
section so as to show what might be preserved within the dorsal 
shell With a knowledge of the character and position of the append- 
ages, as they were buried in the rock, sections might have been cut at 
once revealing all that was desired to prove this knowledge to others. 
But the true conditions were more in this wise. An Arthropod of 
which little was known as to the structure of its appendages was 
buried originally in a soft, calcareous mud or ooze. It was subjected 
to maceration and disintegration by the action of the water, and also 
to the attacks of the small scavengers of the time (Leperditiæ), an- 
tecedent to its burial in, and the consolidation of, its muddy bed. 
In the process of mineralization calcite replaced the viscera and con- 
tents of the appendages, destroying most of the details of structure. 
Taking a specimen that a fortunate blow of the hammer has exposed 
unbroken, the section is cut down through a mingled mass of what was 
formerly the viscera and appendages, if they chance to be present at all : 
that but one specimen in twenty gave an instruotive section is not at 
all surprising. As the work extended over several years, what is now 
known of the structure of the appendages is the result of an accumula- 
tion of material and facts from time to time and not of a fortunate dis- 
covery of one or more instructive specimens. 
In the latter part of the year 1876 a preliminary notice was pub- 
lished of the results then obtained by section cutting.t Conclusions 
were drawn to be abandoned six months later on the discovery of evi- 
dence that negatived them. The following year a further notice of the 
progress of the work was published. t 
The conclusions then arrived at are not all sustained, although the 
main features of the structure of the Trilobite were well recognized. 
This is especially true of the cephalic appendages, showing the affinity 
of the Trilobite with Limulus and Hurypterus. 
Many fine and instructive sections have been cut since 1877 that 
give information in relation to minor points of structure. 
* 205 are from Ceraurus plewrexanthemus, 49 from Calymene senaria, 11 from 
Asaphus platycephalus, and 5 from Acidaspis Trentonensis. 
+ Pamphlet issued in advance of the 28th Report of New York State Museum of 
Natural History. 
$ See 31st Report of New York State Museum of Natural History, p. 61. 
