206 JOURNAL OF SCIENCE. 
Here we have an instance of the imperfection of the evidence 
afforded by paleontology even under the most favourable 
circumstances. 
Burmeister, in the “Organisation of Trilobites” (1843), 
arguing chiefly from the variable number of body segments, and 
from the absence of appendages, came to the conclusion that 
the “ trilobites were a peculiar family of Crustacea, nearly allied 
to the existing Phyllopoda, approaching the latter family most 
nearly in its genus Lranchipus.” Consequently he thought that 
the appendages were soft and membranous like those of 
Branchipus, and that they had in all cascs perished, while the 
hard dorsal shell had been preserved. He _ supported this 
view by asking why the trilobites had the power of rolling 
themselves into a ball, if it was not to protect the soft and 
delicate appendages. In making use of this argument he seems 
to have forgotten that many Isopods have the power of rolling 
themselves into a ball, although they have ambulatory legs 
covered with a moderately hard exoskeleton. 
Up to 1870, nothing more was known about the appendages 
of trilobites. In that year Mr. Billings discovered a specimen 
of Asaphus platycephalus, which appeared to afford evidence of 
the presence of articulated appendages. This was, however, so 
unsatisfactory that Messrs. Dana, Verrill, and Smith rejected 
Mr. Billing’s view, and his discovery has since been ignored by 
many recent authors in zoology. It was in the same year that 
Mr. Woodward, who supported Mr. Billing’s view, announced 
the discovery of the jointed palpus and one of the maxille of 
an Asaphus, in position by the side of the hypostoma. All 
other knowledge that we have on this point is due to Mr. Wal- 
cott’s researches. In 1876 he announced the discovery of the 
natatory and branchial appendages of the trilobites, and in the 
next year he gave additional evidence to show the presence of 
manducatory jaws, ambulatory legs, and branchie in the genera 
Calymene and Ceraurus; and in 1881 he published the paper 
now under consideration, which, he says, “terminates, for the 
present, an investigation that has occupied much time and 
attention during the last seven years.” 
His results were obtained almost wholly from two species— 
Calymene senaria and Ceraurus pleurexanthus, for it was only in 
these species that the appendage, &c., were recognisable. Of 
these species 3,500 entire specimens were obtained from the 
Trenton limestone, at Trenton Falls, N.Y. Out of this great 
number 2,200 were in a condition to warrant sections being made 
of them; but even out of these comparatively few showed 
remains of the appendages, “only 270 sections affording more 
or less satisfactory evidence of their preservation.” 
From these numbers it will be seen that Mr. Walcott’s 
paper, though not very long, is the result of much patient and 
laborious work, and not of the fortunate discovery of a few 
specimens showing the appendages. 
His results are briefly as follows :—The ventral membrane 
