5* 
THE APPENDAGES, ANATOMY, AND RELATIONS OF TRILOBITES. 
1918, pi. 26, figs. 8, 14, 15; pi. 27, figs. 1-3, 5a, 6-9, 12 (not Calymene), (not 15, Calymene) ; pi. 28, figs. 1-5; 
pl. 34, fig- I ; pl- 35, n g- 7-— Milne-Edwards, Ann. Sci. Nat., Zoologie, ser. 6, vol. 12, 1881, pi. 10, figs. 1-18 — 
Bernard, The Apodidse, 1892, text figs. 46, 51. 
Cephalic Appendages. 
No trace of antennules has yet been found. 
I find only three sections cut through the plane of the hypostoma of Ceraurus which 
show anything of the cephalic appendages, and no one of them is very satisfactory. The 
best is No. 22, the one figured by Walcott (pl. 3, fig. 2, 1881; pl. 27, fig. 12, 1918), but 
one should remember that this section is not actually cut in the plane of the hypostoma but 
is a slice diagonally through the head, cutting through one eye and the posterior end of 
the hypostoma. It shows what seem to be the coxopodites of the second, third, and fourth 
pairs of cephalic appendages, the exopodites of the third and fourth pairs, and the metas- 
toma. If this interpretation is correct, the first pair of gnathites lay alongside the hypos- 
Fig. 17. — Transverse section of Ceraurus 
plearexanthemus, showing the relation of 
the coxopodite to the appendifer. Traced 
from a photographic enlargement of the 
slice. Specimen 128. X 4-5- 
Fig. 18. — Slice of Ceraurus pleurex- 
anthemus, showing a nearly continu- 
ous section of an endopodite. and an 
exopodite above it. The latter is so 
cut as to show only the edge of the 
shaft and the bases of a few setae. 
Traced from a photographic enlarge- 
ment. Specimen 111. X 4- 
toma or under its edge, and were feebly developed, the second pair were attached in front 
of the tip of the hypostoma, curved back close to it, and their inner ends reached the sides 
of the metastoma. The third and fourth pairs were back of the metastoma, the third 
pair was stronger than the second, and the fourth probably like the third. 
Specimen 92 shows traces of the slender endopodites belonging to the cephalon, but no 
details. Specimen 22 shows on one side exopodites (epipodites of Walcott) belonging to 
the third and fourth cephalic appendages. That belonging to the third shows some long 
seta? and a trace of the shaft, while the one on the fourth appendage (third coxopodite) has 
a portion of a broad shaft and a number of long seta?. It should again be remembered 
that the slice does not cut through the plane of the exopodite, but across it at a low angle, 
so that a part but not all of the shaft is shown. On the other side of this slice there is a 
fairly good section of one of the thoracic exopodites. It is, however, turned around in 
the opposite direction from the others, as would be expected in an enrolled specimen. 
Specimens 4. and 5 (pl. 1, figs. 4, 5, 1881) are slices cut diagonally through the head 
of Ceraurus, in front of the posterior tip of the hypostoma. They show fragments of 
endopodites and exopodites which may be interpreted as practically identical in form with 
those of the thorax. Due to the diagonal plane in which the section is cut, slice 5 shows 
