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PACIFIC SCIENCE, Vol. XIII, October, 1959 
Fig. 1. Engraulis mordax infected by Caligus klawei sp. nov. X 2.5. 
First antennae two=jointed as usual. Apical 
joint ends in several delicate hairs and two 
thicker spines, and bears a solitary hair at 
about the center of its side. Basal joint tri- 
angular and fringed by three or four rows of 
stout pinnate spines on frontal margin. 
Lunules semicircular, truncate on front side. 
Second antennae three-jointed. Terminal joint 
sharp, strongly curved and carrying two tiny 
spinules, one at the base and the other a short 
distance distally. Basal joint armed with a 
pointed, spurlike posterior process. Mouth 
tube has broad apex, enclosing slender man- 
dibles well dentate on their curved apical 
blade. First maxillae small in size, apex hook- 
like, base oblong and furnished on the sur- 
face with two delicate hairs, each arising from 
a papilla. A similar hair present on the ster- 
num behind the maxilla. Second maxillae 
broad at base, slender toward tip and directed 
straight backward; exopodite made up of one 
longer and two shorter spines. First maxilli- 
peds slender; terminal joint longer than basal 
joint, ending in two unequal claws with 
finely pectinate, narrow rims and carrying a 
narrowly triangular accessory lamina a short 
distance behind. Second maxillipeds cheli- 
form, moderately stout. Their palm fusiform, 
about thrice as long as wide and with a very 
slight bulge at about the center of inner mar- 
gin. Finger straight in its basal half, but termi- 
nating in a strongly curved, sharp claw which 
acts against the bulge of the palm. Claw bears 
two short spines at its base. Sternal furca 
V-shaped, branches uniform in breadth, blunt 
at tip and without marginal rim. 
First swimming legs provided with triangu- 
lar rudiment of endopodite. Protopodite of 
second legs indistinctly divided into two 
joints. Two rami of third legs widely sepa- 
rated from each other by a crescentic dilata- 
tion of basal apron; exopodite two- jointed, 
whereas endopodite is practically one-jointed, 
owing to almost complete reduction of basal 
joint. Fourth legs uniramous, having proto- 
podite longer than two-jointed exopodite. 
Arrangement of spines and setae present in 
each of four pairs of legs is shown in Table 1. 
Of the apical spines on the first legs, the 
middle two are deeply forked into parallel, 
unequal branches; the external branch is 
shorter and has fine pectination on the sides. 
The outermost of them is bifid to a very 
slight extent, and the innermost is simple and 
more than once the length of the others. 
Plumose spines borne on the third joint of 
first legs, on the exopodite of second legs, 
and on the first endopodite joint of the latter 
are rimmed on one side for some distance 
from the base by hairs which are shorter but 
stiffer than those fringing the opposite side 
and other regions. The similar spine on the 
protopodite of second legs is dilated at the 
base into a semicircle, where it bears stiff hairs 
