Lepeophthekus dissimulates-— L ewis 
221 
The protopodite is one-segmented, its greatest 
width about three-fourths of the greatest length; 
the lateral margins are slightly irregular al- 
though generally convex, and the distal margin 
is broadly curved. The exopodite is four-seg- 
mented and attached to the dorsal lateral surface 
of the protopodite although the division be- 
tween the first segment and the protopodite is 
incomplete. The first segment of the exopodite 
is more than 2Vi times the combined lengths 
of the remaining three segments, its lateral mar- 
gins are broadly convex, and the distal surface 
has a concavity in which the proximal end of 
the second segment is attached. A single lightly 
plumose seta is present on the distal portion of 
the inner lateral surface of the first segment. 
The second segment is short, its greatest width 
about equal to the greatest length; the distal 
surface is slightly concave and receives the 
proximal end of the third segment. A single 
seta is present on the distal portion of the inner 
lateral surface of the second segment. The third 
segment is slightly longer than the second and 
flared from the narrow proximal to broader dis- 
tal end; the distal surface also has an irregular 
concavity for the proximal end of the fourth 
segment. A single seta is present on the distal 
portion of the inner lateral surface of the third 
segment. The fourth or terminal segment is 
minute and rodlike, with a concave distal sur- 
face that receives the base of the slightly plu- 
mose terminal seta. The endopodite is two- 
segmented and attached to the ventral lateral 
surface of the protopodite although the division 
between the first segment and the protopodite 
is incomplete. The first segment is approxi- 
mately 1 Vs times the length of the second, the 
lateral margins are slightly irregular, and the 
distal end is flared slightly and bearing a small, 
pointed protrusion on the anterior distal corner. 
The second segment has slightly irregular lateral 
margins, the distal end is slightly broader than 
the proximal, and the distal surface is flat and 
bears two lightly plumose setae. 
The mandible of the second nauplius (Fig. 
1 6b) is similar to that of the first nauplius. The 
first segment of the exopodite is, however, 
longer than that of the preceding stage, being 
more than 3 Vi times the combined lengths of 
the remaining three segments. The small pointed 
protrusion on the anterior distal corner of the 
first endopodite segment of the first nauplius is 
larger in the second nauplius and projects an- 
teriorly although there is some variation in size 
in different specimens. 
The copepodite mandible (Fig. 1 6c) is uni- 
ramous and four-parted as in the adult. The ap- 
pendage is attached to the ventral surface of the 
cephalothorax just lateral to the division be- 
tween the well-developed membranous hyper- 
stome and hypostome and projects through the 
division into the mouth cone. All four parts are 
heavily sclerotized and indistinctly divided, the 
division often appearing only as a light area. 
The first part is approximately twice the length 
of the second, tapered slightly from the proximal 
to the narrower distal end. The second part is 
strongly tapered from the first to slender third 
part. The third part is elongate, the length 
slightly less than the combined lengths of the 
first two parts; the lateral margins are almost 
parallel. The fourth part is short, the length less 
than one-half that of the third part. The fourth 
part is also angled medially; there is no curva- 
ture as the fourth part of later stages has. The 
fourth part is tapered to a sharp point distally; 
the inner margin is lightly serrated but does not 
have the denticulations visible in the adult. 
The condition exhibited by the copepodite 
mandible is changed but little in the chaiimus 
stages. The only part that changes to any extent 
is the fourth part, the other three changing only 
slightly in their relative lengths. A slight curva- 
ture of the fourth part is visible in the first 
chaiimus (Fig. \6d) y this curvature becoming 
greater throughout the remaining chaiimus 
stages (Fig. iGe-i) so that the fourth part is 
evenly curved in the sixth chaiimus and adult 
(Fig. 1 6i, ;). Further modification of the fourth 
part is from the sharply pointed condition of 
the copepodite to the bluntly rounded tip of 
the adult and the gradual appearance of the 
denticulations present on the inner surface of 
the adult. 
Mouth Cone 
The mouth cone is first exhibited by the co- 
pepodite, although a slight swelling is visible 
on the second nauplius that may be the begin- 
ning of this structure. The cone itself is formed 
of two membranous structures, a hyperstome 
and hypostome, that are usually closely applied 
