MUSEUM OF COMPARATIVE ZOOLOGY. 193 



The sections of the Trilobite retained in the slices of rock are trans- 

 hicent, and in nearly all cases when used for illustration were photo- 

 graphed by transmitted light. The photographs were used to obtain 

 the outlines of the dorsal shell and appendages, thus insuring a greater 

 degree of accuracy than enlargement by measuring. 



In referring to what has been done in the past, in the study of the 

 organization of the Trilobite, it is unnecessary to present the many 

 strange views that have been advanced to show that it was related to 

 fish, mollusk, insect, or some crustacean to which it has but a superficial 

 resemblance. These are given in the introduction to the study of the 

 " Organization of Trilobites," by H. Burmeister, where the student 

 can find the most complete review of the subject up to the date of the 

 English edition (1846) that has been published. M. Barrande, in the 

 Supplement to his Volume L, 1872, presents an historical review to 

 that time. 



The following historical notes are given as showing that many 

 naturalists have considered the Trilobite related to Limidus and also 

 to the Phyllopoda as represented by Apus and BrancJiipus. 



1750. Ch. Mortimer, in the Philosophical Transactions (XL VI. 

 p. 600), expressed the opinion that Scolopendrce aquaticce scutatCB 

 affine animal petrificatum (the Trilobite) appeared to correspond with 

 Monoculus apus, Linn. 



1753. Linnaeus designated all the species belonging to the Trilobite 

 as modifications of his Entomolithus paradoxus, deciding himself in 

 favor of their near affinity to Monoculus apus. This view is expressed 

 in all the editions of the " Systema Naturae." 



1768. Ch. Fr. Wilkens sustained the views of Linnaeus, and gave 

 the name Entomolithus hrachiopodus cancriform,is marinus, thus 

 removing the Trilobite from the domain of conchology, to which it had 

 frequently been referred. 



1771. J. Imm. Walch adopted Wilkens's views, and, convinced of 

 the unsuitableness of the name heretofore used, gave the name Trilo- 

 bite, a designation that was generally received, and has since been used 

 by authors with the exception of Dalman. 



1821. H. Burmeister says that " the year 1821 is a crisis in the 

 literary history of the Trilobite, for a new epoch then commences," 

 V. Audouin and George Wahlenberg both arriving at very important 

 results in their studies. Audouin summarizes his results in the follow- 

 ing four conclusions, viz. : — 



1st. That Trilobites differ only from the other Articulata in points 



