The VeiUral Slrycfare of Triayfhni.s. — JJcccher. 95 
distinctl}' traced, though their presence is indicated on plate 
IV, figure 1, where, on the left side, there are endopodites and 
exopodites in sutticient number for each appendage of the 
head. That these should be referred to the cephalic limbs is 
further indicated b}^ their being in advance of the endopodite, 
which manifestly pertains to the first thoracic segment. The 
inner edge of the mandibles as well as that of the other gnath- 
obases of the head is apparentl}^ finely' denticulate, as shown 
on plate iv, figure 1, and plate v, figure 2. 
Third (Old fourth hf'raiitoiis apj)euda<j('s, or inaxiJla'. Fol- 
lowing the appendages referred to the mandibles are two pairs 
of strong limbs, with broad plate-like basal i)ortions, or coxop- 
odites, serving as gnathites (plate v, figures S-11). They 
resemble each other, and are similar in form to the two pre- 
ceding limbs, though somewhat larger. They are usually 
fairly well preserved and their form and structure can be ap- 
proximately made out. The endopodites are composed of 
stout joints, and could be extended but a short distance be- 
yond the margin of the head. The exopodites are more slen- 
der and carry an abundance of stiff sette, which often diverge 
in a fan-like manner from their line of attachment. These 
brushes of seta- occupying the cavities of the cheeks are often 
preserved in specimens where the other details of the limbs 
are obscure or obliterated. In Triorthrus they are evidently 
homologous with similar brushes observed by Walcott in 
Cdly inene* 
This completes the number of paired appendages which can 
be definitely referred to the head. It is evident they do not 
differ conspicuously from each o^her, and, as will be presently 
shown, they closely resemble the thoracic legs in all essential 
structural characters. 
Thoracic legs.' In the paper by the writer ( 1. c.) describing 
the structure of the thoracic legs, the endopodites and exopo- 
dites of the second and third pairs were illustrated, together 
with their points of attachment. The form of the coxopodite, 
or basal porrion, was at that time unknown. \\"\i\\ the present 
material it is possible to add several details. The most im- 
portant are the inward prolongation of the coxopodite of each 
*Thp Trilohiu-: New iiiul Old Evidence rcljiliiii;' to its Or^'iini/alion. 
Bull. Miis. Comp. Zool.. vol. viii, No. K). ISSl. 
