VIIl 
APPENDAGES 23 
N 
each consisting of a single flagellum formed of short conical joints. 
The other cephalic ap- 
pendages increase in 
size successively. At 
present the second and 
third pairs are not 
satisfactorily known, 
but appear to have 
been similar to the 
fourth and fifth pairs. 
The second pair is 
attached at the level 
of the posterior end 
of the hypostome. The 
fourth and fifth pairs 
have large, triangular 
coxopodites which 
served as gnathobases, 
their inner edges being 
denticulate ; the endo- 
podites consist of stout 
joints; the exopodites 
are slender, and bear 
setae which are often 
arranged in a fan-like 
manner. 
The first pair of 
appendages appear to 
be antennules, whilst 
the second pair prob-. 
ably represent the an- 
tennae, the third pair 
the mandibles, and the 
fourth and fifth pairs 
the maxillae of other 
Crustacea. The append- 
ages of the thorax and 
pygidium do not differ 
essentially from the two 
posterior cephalic appendages. 
Fig. 142. — Triarthrus 
~ is 
— / Zg 2 
aS Z <2) jo 
BN. ZG oa 
va sat ae A ee 5 NN pote 
gis ean : nee NSS 
Gus Bee ees ve ey 
Y Ziel a i cos 
“ih IZ oo set aS x 
tg ie gl cen oN a ae wna 
QF es aw 
Ci) Dh reat Gage pagans 
i ee w= Tail SS 
ye ‘Ws Nhs S 
Gres ZS . 
he ps ians STH - A i\ 
e LoS ek Nn hi 
ihe pl Ad aN Z De 
Wend det 
Mbt 
rib 
Ve, AVA, } 
f\ NR | 
( (ony 
Vay 
becki, Green, x 24. Utica 
Slate (Ordovician), near Rome, New York. A, 
Ventral surface with appendages ; Hp, metastome ; 
Hy, hypostome. B, second thoracic appendage ; 
en, endopodite ; ex, exopodite, x 12. (After 
Beechey. ) 
Those on the anterior part of 
