NE0LENUS. 
2 9 
For convenience of discussion, these lobes may be called Nos. I, 2, 3, and 4, the last 
being the posterior one (fig. 5). This lobe is best shown on the matrix, where the anterior 
end is seen to be margined by stout spines, while the posterior end lies over the endopodite 
and under the exopodite behind it. No. 3 is sunk below the level of the others, and only 
a part of it has been uncovered. Its margin bears strong spines of different sizes. Its 
full shape can not be made out, but it has neither the shape nor the form of spines shown 
in figure 3, plate 20 (1918). Lobes 2 and 1 and another lobe in front of 1 seem to form 
a continuous series and to be part of a single appendage. They are all in one plane, are 
so continuous that the joints between them can be made out with difficulty and if they do 
belong together, can easily be explained. 
Fig. 5. — A sketch 
of the so-called 
exites of Neolenus 
serratus (Rom- 
inger), to show the 
form and the char- 
acter of the spines. 
X2. 
Fig. 6. — Endop- 
odite of a cephalic 
appendage of Neo- 
lenus serratus 
(Rominger), show- 
ing the very broad 
coxopodite. X 2. 
Before calling these structures new organs not previously seen on trilobites, it is of 
course necessary to inquire if they can be interpreted as representing any known structures. 
That they can not be exopodites is obvious, since they are bordered by short stout spines 
instead of sete. The same stout spines that negate the above possible explanation at once 
suggest that they are coxopodites (compare fig 6). At first sight, the so-called exites seem 
too wide and too rounded to be so interpreted, but if reference be had to the specimens 
rather than the figures, it will be noted that the only well preserved structure (No. 2) is 
longer than wide, has spines only on one side and one end, and does not differ greatly 
from the coxopodite of specimen No. 58589 (pi. 18, 1918). If structures 2, 1, and the 
segment ahead of 1 are really parts of one appendage, it can only be an endopodite, of 
which No. 2 is the coxopodite, No. 1 the basipodite, and the next segment the ischiopo- 
dite. If one looks carefully, there are no traces of spines on either end of No. 1, but only 
on the margin. The extreme width of No. 2 is against this interpretation as a coxopo- 
dite (see, however, fig. 6), but it may be rolled out very fiat, as this is an unusually 
