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 (Leperditice), 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 instructive 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 j-ear 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. J 



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 Eurypterus. 



Many fine and instructive sections have been cut since 1877 that 

 give information in relation to minor points of structure. 



* 205 are from Ceraurvs plcKrexanthcmus, 49 from Cahjmene senaria, 11 from 

 jisaphics platycepkalus, and 5 from Acidaspis Trcntonensis. 



t Pamphlet issued in advance of the 28th Report of New York State Museum of 

 Natural History. 



X See 31st Report of New York State Museum of Natural History, p. 61. 



