hepeophthewus dissimulatus— L ewis 
223 
nected to the same poorly defined plate from 
which it arises. 
The postoral process of the first chalimus 
(Fig. 1 6s) is distinctly different from that of 
the copepodite. The process consists of a two- 
parted, spinelike process and a setule-bearing 
nodule, both attached to a well-defined plate just 
lateral and posterior to the base of the mouth 
cone and contiguous with the plate present at 
the base of the cone. The two-parted, spinelike 
process projects posteriorly; both parts are 
rounded distally, the second part being attached 
to the distal end of the first. The greatest length 
of the second part is approximately two-thirds 
that of the first. The setule-bearing nodule is 
just anterior to the base of the spinelike process, 
at the anterior end of the plate. The nodule is 
small and gives rise to two slender setules from 
its distal surface. 
A general transition is apparent from the first 
chalimus to the adult. The two-parted condition 
of the postoral process is still evident in the 
second chalimus (Fig. 16/), but in the third 
(Fig. 1 6u) the two parts become fused, the 
distal portion becomes more sharply pointed, 
and the base spreads out to its greatest width, in 
the adult (Fig. 1 6y), the width in the adult 
being just slightly less than the length. The plate 
from which the process and the setule-bearing 
nodule arise becomes indistinct in the second 
chalimus, third chalimus, and fourth chalimus, 
then becomes more distinct in the fifth chalimus 
but appears as two parts. These two parts of the 
plate are evident in the sixth chalimus and in 
the adult. The anterior plate has a posteriorly 
directed lobe (within, not projecting from, the 
cephalothorax ) just medial to which the setule- 
bearing node projects. The posterior plate forms 
the base of the spinelike process and is continu- 
ous with it. The setule-bearing node enlarges 
somewhat throughout development and adds 
another setule to its armature, having two slen- 
der setules in the second chalimus, three in the 
third and fourth chalimus, two (?) in the fifth, 
and three in the sixth chalimus and in the adult. 
All the setules are borne on the distal surface 
of the nodule. 
Maxilla 
The term "maxilla” is applied to the pair of 
oral appendages immediately behind the mouth 
cone and postoral processes. This appendage 
pair has gone under a variety of names because 
of the terminology applied to the postantennal 
and postoral processes. Inasmuch as the term 
"process” is here applied to the postantennal 
and postoral structures, the first pair of recog- 
nizable appendages behind the mouth are des- 
ignated as the maxillae. 
The maxilla is first present in the copepodite 
(Fig. 17*) and is found attached to the ventral 
surface of the cephalothorax just posterior and 
lateral to the postoral process. The first segment 
of the two-segmented structure is strongly de- 
veloped; the proximal surface possesses a medial 
projection that articulates with the cuticle of 
the body at the point of attachment of the ap- 
pendage. The distal margin of the first segment 
is flat; the surface is depressed and receives the 
proximal surface of the second segment. The 
second segment is elongate, being slightly longer 
than the first segment and much thinner. The 
lateral margins of the second segment are irreg- 
ular, the outer proximal margin curving inward 
to the irregular proximal surface, the inner mar- 
gin with several flatly convex swellings. The 
distal region of the second segment is slightly 
swollen, the distal margin broadly rounded. 
Two processes are present on the distal region 
and extend out from the segment. The outer 
process is spinelike and is less, than one-fourth 
the length of the segment; this process possesses 
a series of minute, tine-like projections along 
the inner margin giving it a brushlike appear- 
ance. The inner process arises from the posterior 
lateral surface of the distal region, not the dis- 
tal surface as does the outer process; it is lobate 
and flimsy in nature, its length approximately 
equal to that of the outer process. 
The segments of the maxilla of the first chal- 
imus (Fig. 17 h) are similar in general make-up 
to those of the copepodite. The proximal articu- 
lation surface of the copepodite appendage is, 
however, absent in the first chalimus and, fur- 
ther, the first segment is somewhat thicker. The 
distal surface of the first segment is concave 
and forms the articulation surface for the ball- 
shaped proximal end of the second segment. 
The inner of the two terminal processes on the 
second segment is slightly longer than the outer 
and is tapered to a sharp point. The outer of 
the two processes is simple and lobate, lacking, 
