10 
J. M. Thomson. 
Percival, E., 1937: New species of Copepoda from New Zealand Lakes. Bee . 
Cantab. Mas. Y T ol. 4, No. 3, pp. 169-176. 
Wilson, C. B., 1932: Copepods of the Woods Hole Region. U.S. A at . Hus Bull., 
158, pp. i-xix, 1-635. 
Order: IIARPACTICOIDA. 
Family: CANTHOCAMPTIDAE. 
MESOCHRA Boeck 1864. 
Mesochra parva sp. nov. 
Occurrence. 
A few specimens were collected throughout the year, hut they were 
extremely abundant in October and November, among shallow-water algae. 
F EM ALE. 
Length 0.45 mm. Body with genital segment divided. Abdominal 
somites without spines on the dorsal surface, but each has a lateral row 
of spines which is continued on to the ventral surface for a short distance. 
On the anal segment these are particularly small and they are not markedly 
separated from the spines lining the margin of the anal incision. The anal 
operculum is spineless. Caudal rami broader than long; outer terminal seta 
less than half the length of the inner seta, which is less than half as long 
as the body. 
Appendages: First antenna. 7-segmented; third segment the largest, 
bearing a tufted spine. The aesthetasc is on the third segment and extends 
for a short distance beyond the end of the appendage. Second antenna has 
basal segment elongate and narrow, undivided; exopod 1-segmented with two 
apical and one lateral setae, of which the outermost is the shortest and 
stoutest ; endopod large and expanded somewhat distally, with four terminal 
setae, one smaller than the others, and on the outer margin a row of four 
to six spinules. Mandible with palp two jointed and with three distal setae. 
The remaining mouth parts are characteristic of the genus. Maxillipeds, 
subcheliform, with a seta on the basal segment near the distal end. 
Natatory limbs. Legs 1-4 with 3-segmented exopods and 2-segmented 
endopods. The first legs have the basal segment of the endopod consider- 
ably longer than the exopod. It bears an inner marginal seta slightly 
proximal to the middle of the segment. The distal segment of the endopod 
bears two stout setae. The basal segment of the exopod has an inner seta. 
The arrangements of spines and setae are shown in the figures. 
Setae formula. 
Endopod 
p2 1 221 
p3 1 221 
p4 1 221 
Exopod 
0 1 122 
0 1 222 
0 1 222 
Fifth leg with basal segment extending beyond the distal and bearing five 
setae. The distal segment is distinctive, almost quadrangular w ; th two stout 
setae at the distal corners, the inner twice as long as the outer. Next to 
the inner spine is a very slender seta. Between the setae are minute spinules. 
