226 
around the distal end and distal lateral margins. 
Both segments of the maxilla of the fifth 
chalimus female and male (Fig. 17/) are more 
slender and appear more elongate than those of 
the preceding stage. The first segment is slightly 
shorter than the second and its proximal end 
projects as an irregular, lobate articulation proc- 
ess. The outer margin of the segment is flatly 
convex; the inner is slightly convex proximally, 
flat medially and concave distally. The outer dis- 
tal margin is tapered abruptly to a knoblike pro- 
jection of the inner distal surface that appears 
to be the enlarged projection of the distal end of 
the first segment of the fourth chalimus. The 
second segment is slender, the proximal end 
two-parted and included in the inner lateral 
margin. The junction of the two parts of the 
proximal end forms a concave surface that ar- 
ticulates on the knoblike process on the distal 
end of the first segment. The outer lateral mar- 
gin of the second segment is generally flatly 
convex; the inner lateral margin is slightly ir- 
regular, with a slight indentation in the middle 
that bears a single spinule and a fine membrane 
connected to the spinule and extending proxi- 
mally for a short distance. The distal end of the 
second segment is almost flat and bears two 
terminal processes. The inner terminal process 
is relatively longer than in the preceding stage, 
being 17/2 times the length of the outer process; 
the outer margin is fringed with a fine, lightly 
frilled membrane. The outer process is lobate 
and covered with minute, hairlike projections. 
The maxilla of the female and male sixth 
chalimus (Fig. 17g) is similar to that of the 
fifth chalimus in general shape. The segments, 
and especially the proximal projection of the 
first segment, are heavier; the knoblike projec- 
tion of the inner distal surface is on the inner 
corner so that it forms the junction of the inner 
lateral and inner distal surfaces. The proximal 
end of the second segment, included in the in- 
ner lateral surface, again appears two-lobed, the 
proximal lobe extending proximally and form- 
ing the point of attachment for the muscle that 
abducts the second segment. The distalmost of 
the two lobes forms an indentation in the mar- 
gin that extends for a short distance although 
there is a continuation, as a distinct line of di- 
vision between the two lobes, running almost 
parallel to the lateral margins of the segment. 
PACIFIC SCIENCE, Vol. XVII, April 1963 
The middle of the lateral surface of the second 
segment is tapered slightly but abruptly; the 
spinules and membrane present in this region 
in the adult and in the preceding stage were not 
present on any of the specimens examined. The 
two terminal processes on the flat distal end of 
the second segment are both slightly larger than 
in the preceding stage; the outer is now pointed 
distally and both have a fine, membranous mar- 
gin along their inner and outer surfaces. 
The maxilla of the adult female and male 
(Fig. 17 h) is more definitely shaped than any 
of the preceding stages and the first segment 
more strongly developed than in the preceding 
two chalimus stages. The first segment is short 
and stocky, the inner proximal end protruding 
as an irregular articulation surface. The distal 
lateral margins of the first segment are tapered 
irregularly to the somewhat narrow distal sur- 
face, the median portion of which projects as 
a narrow, lobate articulation surface that is heav- 
ily sclerotized. The second segment is elongate, 
the lateral margins irregularly convex. The 
proximal surface, included in the inner lateral 
surface, is irregular, with a slight concavity that 
forms the place of articulation for the medial 
projection of the distal surface of the first seg- 
ment. The middle of the inner margin is notched 
in two places, the proximal notch bears a minute 
spine not present in any preceding stage, and 
the distal notch bears a larger spine, about twice 
the length of the proximal spine. A fine mem- 
brane is also present and connects the two 
spines. The two terminal processes arising from 
the step-shaped distal end of the second seg- 
ment are more elongate than those of the pre- 
ceding stage. The innermost of the two proc- 
esses is about \ l /2 times the length of the outer 
and possesses a membrane along the outer mar- 
gin. The outer process is fringed by a frilled 
membrane along the outer margin. 
Maxilliped 
The maxillipeds have been termed the first 
thoracic appendages in copepods as well as in 
other crustaceans and the maxillae as the last 
cephalic appendages (Borradaile et aL, 1958: 
347-348 ) . This terminology is accepted by most 
authors, including those who apply the term 
"first maxilla” to the postoral process, but is 
not accepted by those workers who call the post- 
