T eredicola typica — W ilson 
271 
Edmondson can be accounted for by their 
inclusion of the intersegmental membrane of 
the genital segment, which is very broad in 
fully expanded specimens. The integument 
of the urosome is relatively thin and in the 
whole lot of preserved specimens that I have 
examined there was a dominant tendency for 
prominent expansion of all the segments as 
shown in Figure 3. There is no striking differ- 
entiation between the segmental margin and 
its membrane and the number of true seg- 
ments could easily be misinterpreted. 
In the lot of specimens examined, only one 
was found in which the segments of the uro- 
some were fully contracted. Between this con- 
dition and the fully expanded specimens, 
intermediates were found. True length meas- 
urements of individual specimens are there- 
fore difficult to achieve. There is, however, 
no doubt that there are considerable real as 
well as superficial differences in total length 
between specimens. From my observation, 
the range of length measurements given in the 
literature is reasonably accurate (female, from 
about 4. 0-5.0 mm., male, 1.75-2.35 mm.). 
Because of the variation found in the shape 
of the cephalic segment in both sexes, ex- 
amples of the extremes of these conditions 
were particularly examined in detail for possi- 
ble correlated differences in both body and 
appendages, but none were found. 
The caudal rami exhibit many degrees of 
divergence in both sexes and it seems evident 
that this divergence results from an extremely 
flexible attachment rather than from any real 
individual or sexual variability. No sexual 
dimorphism was found in the number or rela- 
tive size of the caudal setae, although as 
happens in all copepods, they were at times 
broken. Most of them are very slender and 
can be observed accurately only at high mag- 
nification. 
No variation was found in the segmentation 
of the antennuie. Both Wilson’s figures and 
his statement that the basal segment is non- 
setiferous, points to his inclusion of the sur- 
face eminence to which the antennuie is 
attached, giving six rather than five segments. 
When his illustrations are interpreted as 5- 
segmented antennules, the relative lengths of 
the segments correspond closely to those 
given here, the second segment being much 
the longest. 
Wilson neither figured nor described the 
actual antenna. In the text, it is mentioned 
only in the generic diagnosis of the male, in 
which it is described as "2-segmented, pre- 
hensile.” His figure labeled "second antenna 
of female” is obviously either the second 
maxilla or the maxilliped of the female, prob- 
ably the latter. No other cephalic appendages 
were described. 
It is impossible to accept as a variation or 
to explain Wilson’s observation that two 
outer setae (or short spines) are present on the 
first exopod segments of the legs, instead of 
the one spine observed in all my dissections. 
In the Copepoda, two spines have been found 
on this segment only in the Platycopiidae, 
a family far removed from these cyclopoid 
parasites. It is difficult to accept this even as 
an anomaly, nor is there present any cuticular 
spinous production of the segment itself to 
allow for misinterpretation. Otherwise, Wil- 
son’s figures agree fairly well with the legs 
examined in this study, though neither the 
asymmetry nor the variation in the number 
of setae was noted. 
The number of spines on the second exo- 
pod and endopod segments of the legs ap- 
pears to follow a pattern, but even this may 
be disturbed as shown by the female specimen 
in which one exopod of leg 1 and one endo- 
pod of leg 2 had the usual spinal number 
reduced (Table 1). Asymmetry of setation was 
the rule in the females dissected, no individual 
being found with right and left rami alike in 
both legs. Though two males had both pairs 
symmetrical, the two specimens did not com- 
pletely agree with one another. It is evident 
from these observations that the setal formula 
can be used for specific differentiation in this 
genus only upon examination of several 
specimens. 
