HISTORICAL REVIEW. 
The beginning of the search for the limbs of trilobites was coeval with the beginning 
of scientific study of the group, knowledge of the appendages being essential to the proper 
systematic allocation of the animals. 
The early search was so barren of results that negative evidence came to be accepted 
as of positive value, and it was for many years generally believed that such organs as may 
have been present beneath the dorsal test were so soft as to be incapable of preservation. 
This view is best expressed by Burmeister (1846, p. 43) : 
There is good proof that the feet of trilobites must have been soft membranous organs, for the absence 
of the slightest remains of these organs in the numerous specimens observed is of itself evidence of the fact, 
and it can indeed scarcely be supposed that hard horny extremities should be affixed to a soft membranous 
abdominal surface; since they would not have possessed that firm basis, which all solid organs of locomotion 
require, in order that they may be properly available. 
Very well reasoned, and were it not for the discovery of new material in American local- 
ities, 'Burmeister's views would probably never have been proved incorrect. One can not 
escape the suspicion that some of the accepted hypotheses of today, founded on similar 
"proof," may yield in time to the weight of bits of positive evidence. 
The history of the study of appendages of trilobites may be divided into two periods. 
The first, in which there was a general belief that the appendages were soft organs, but 
during which numerous "finds" of limbs were reported, extended from the time of Linne 
to the year (1876) in which Walcott demonstrated the fact that the animals possessed 
jointed ambulatory and breathing organs. 
The second, much more fruitful period, began with Walcott' s publication of 1881, 
descriptive of the appendages of Ceraurus and Calymene, and for the purposes of this 
memoir, closes with his great contribution on the anatomy of Neolenus (1918). Beecher's 
brilliant productions came in the middle of the second period. 
In the first period, there were at least two authentic discoveries of appendages, those 
of Eichwald (1825) and Billings (1870), but since neither of these men convinced his con- 
freres of the value of his finds, the work of neither can be considered as having marked an 
especial epoch in the history. 
As all the authentic finds will be treated in detail on later pages, only a brief resume 
of the first period will be given here. This has already been done by Burmeister (1843, 
1846) and Barrande (1852, 1872), whose works have been my primary sources of informa- 
tion, but I have looked up the original papers, copies of nearly all of which are to be seen 
in the libraries in Cambridge and Boston. Brig.-Gen. A. W. Vogdes, U. S. A. (retired), 
has very kindly placed at my disposal a number of references and notes. 
Linne (1759) was the first to report the discovery of appendages of trilobites. Torn- 
quist (1896) has pressed for a recognition of the contribution of the great Swedish natu- 
ralist to this problem, but Beecher (1896 B) doubted the validity of the find. Linne figured 
a specimen of Parabolina spimdosa (Wahlenberg), with what he interpreted as a pair of 
antennas attached. lie states (translation quoted from Tornquist) : "Most remarkable in 
this specimen are the antennae in the front, which I never saw in any other sample, and 
which clearly prove this fossil to belong to the insects." Beecher has shown as conclusively 
as can be shown without access to the original specimen that the supposed antennas were 
really only portions of the thickened anterior border, the appearance being due to imperfect 
preservation. Briinnich as early as 1781 called attention to the imperfection of this speci- 
