30 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 120 
diandra, but it should be pointed out that the list in table 6 represents 
less than half of the described species. 
The presence or absence of head-hooks in pontellids, and especially 
in Labidocera, has been widely regarded as a feature of considerable 
taxonomic significance. Obviously, if head-hooks can vary in oc- 
currence intraspecifically, their usefulness to phylogeny hinges upon a 
thorough survey of all species in the genus. Head-hooks are found in 
other pontellid genera (Anomalocera, Pontella, Calanopia, Ivellopsis, 
Epilabidocera) but not necessarily in all species of these genera. 
They are characteristically absent in two other genera (Pontellopsis, 
Pontellina). Based on this distribution, head-hooks may be regarded 
as an older generalized feature that is losing adaptive value in some 
of the younger phyletic lines. Certainly, revision of Labidocera is 
Labidocera diandra, co’, St. Y 
C = | individual 
station 
F-5 
ST 
Pe Ue eT ST TT ae See a ee a ea ie eel el eee ee aS po 
station 
F-2 
Noy alee Ts Vie elber i cI e (Ee pec aT of 
1 AA SA AL SUS 
186 1:94 2,02 32:10) 218 226 
I | 
ll eal eGo, 4S) s53lbe 57) 6 65! 1,70 1.78 
390 430 .470 .510 550 590 630 670 173 181 489 197 205 213 221 229 
Right P5 Length (mm) TL (mm) 
Ficure 12.—Size distribution of right leg 5 (P5) and total length (TL) in male Labidocera 
diandra, stage V copepodites, collected at stations F2 and F5 (horizontal hatching= 
morph B males; heavy line=morph A males; specimens selected at random and measured 
at 60X magnification). 
not merely a matter of grouping species according to (1) the presence 
or absence of head-hooks in adults and (2) urosomal segmentation in 
adult females, as suggested by Sewell (1956). Not only are head- 
hooks undependable but the urosome is variously two and three 
segmented in head-hooked and nonhead-hooked species alike. 
