1(4 21ie America a Geologisf, February, 1895 
iiig forward, at first cliveri^'iii^' Tor half tlicir length and then 
slightly converging (plate v, figures 5, 6, 7). 
Paired biritrnoitti (ippendfKjes. 
The remaining paired appendages of the trilobite all seem 
to be biranious, and agree closely in their general features. 
Adjacent members of the series present very slight differences. 
It is only when the primitive and simple phyllopodoiis legs of 
the pygidiiim are compared witii tlie anterior thoracic or ce- 
phalic appendages that variations of note can be observed, al- 
though these are of form and not of structure. On this ac- 
count, there is no well-defined separation into posterior 
antennae, mandibles, maxilhe, maxillipeds, thoracic, and ple- 
opodal appendages. It is most convenient, therefore, to num- 
ber them from before backwards, and to indicate homologous 
positions with other Crustacea only when there is some evi- 
dent reason for so doing. 
First pair of biraiitoiis aj)]tciH/a(/es, or j)osterior anie)nia\ 
The second pair of appendages, corresponding to the pos- 
terior antennie, are attached to the head at each side of the 
glabella, on a line vi^ith the extremity of the hypostoma. They 
are apparently biramous, and thus agree with the second pair 
of nauplian limbs and with the typical posterior antennae of 
many Entomostraca and Malacostraca. The}'' may be com- 
pared with the posterior antennae in Euph((tisi<( pellucida, one 
of the schizopods, especially with the FirrciUa and Cijrtopia 
stages. The details of the endo))odite and expodite are not 
clearly shown. The former is more commonly preserved, and 
its distal joint extends just beyond the edge of the carapace. 
The coxopodite is developed into a triangular plate, the inner 
angle carrying a masticatory ridge, the whole extending about 
three-fourths the distance from the side of the glabella to the 
median line, just below the hypostoma, and directed obliquelj'' 
backwards (plate v. figures 8-H). 
Second pair of biramous a/>pei)da(/es^ or riunidibles. The 
appendages here correlated with the mandibles are immedi- 
ately behind the first pair of biranious limbs. The proximal 
portion, or coxopodite, is similar in form to the preceding, 
though somewhat smaller, and overlapping its basal part. The 
palps, or endopodial and exopodial branches, have not been 
