196 BULLETIN OF THE 
and Latreille. The facts brought together by Mr. Billings added to 
the homology with Limulus, and this was strengthened by the 
observations of Packard in his discussion of the classification of the 
Branchiopoda, and, later, by the writer in discovering the structure 
of the cephalic appendages. 
The instances of the discovery of parts of the animal other than 
the dorsal shell and hypostoma are rare. M. Barrande, in reviewing the 
reported discoveries made of the appendages of the Trilobite to the date 
of the publication of his Volume I., 1852, says : * Unhappily all these re- 
searches have resulted in nothing more than the discovery of the pieces 
of the mouth named Hypostoma and Epistoma, and the intestinal 
canal" Again, in his Supplement to Volume I., 1872, he says: “The 
few scattered observations of parts found which might belong to 
the Trilobites have little value and were accepted as such by natu- 
ralists." 
“Though disposed to regard these processes figured by Mr. Billings 
as feet, still the proof is unsatisfactory." * 
“No traces of ambulatory or natatory limbs of branchiæ or antennæ 
have ever been discovered. .... Quite recently; however, a specimen 
of a Trilobite has been discovered in which it is said that the bases of 
the legs were distinctly recognizable." T 
“No remains of legs are found with any Trilobites, which would 
not be the case if they had stout legs common to crustaceans of the 
same size.” f 
“Up to this time, no certain indications of the existence of append- 
ages, nor even of any hard sternal body-wall, have been discovered, 
though a shield-shaped labrum, which lies in front of the mouth, has 
been preserved in some specimens." $ 
The following appear to be the only instances of the actual discov- 
ery of some portions of the appendages and structure beneath the 
dorsal shell.  . 
1828. M. Goldfuss. As shown in the illustrations, the sections of 
Phacops figured on Plate II. (Annales des Sci. Nat., Tome XV.) appear 
to indicate some remains of appendages. M. Barrande, however, thinks 
that M. Goldfuss failed to prove that the parts he considered as 
branchial feet were anything more than the result of a defect in the 
homogeneousness of the rock, or a section of some fragments gathered 
* Development of Limulus polyphemus. Packard, 1872. 
+ Manual of Zoólogy. Nicholson, 1876. 
t Manual of Geology. Dana, 2d ed., 1876. 
8 Anat. Invert. Animals. Huxley, 1877. 
