
44 RECORDS OF THE S.A. MUSEUM 
PoECILOSTOMA. 
One of the chief distinguishing features of this group of Cyelopoids, aceord- 
ing to Sars (1917, p. 142), is the absence of any structures representing the man- 
dibles of other copepods. He discusses this point at some length and states that 
the most anterior oral appendage is the maxilla (maxillule) bearing a palp which 
has been erroneously taken for an independent limb by other authors who have 
described them as mandible and maxillule. He points further to the resemblance 
between what he terms the maxilla in the families Clausidiidae and Cyclopidae; 
in the latter the mandible is always present but often without a palp, whereas 
the maxillule (his maxilla) always has a palp and is of similar structure to that 
found in the Clausidiidae. He admits, however, that ‘‘in a few cases this exopo- 
dite may assume a somewhat maxilla-like appearance.’’ 
In this connection | find myself in complete disagreement with Sars, at 
least as far as the Clausidiidae is concerned. The few specimens of H emicyclops 
found in this collection have been dissected with particular attention as to whe- 
ther these two anterior pairs of mouth parts came away together or were at- 
tached separately. In each case I found no attachment between them and dur- 
ing dissection observed that they were independently mounted side by side on 
the supporting skeleton. I am, therefore, convinced that there are two separate 
appendages: the mandible, which has the typical shape of such an appendage 
though lacking a palp and having a somewhat specialized armature and the maxil- 
lule, which is here distinetly cleft, the smaller lobe armed with strong spines 
representing the gnathobase, the larger lobe with setae only being the palp. Sars, 
in support of his view that there is only one appendage, the maxillule, states 
that ‘‘the said limbs are not placed, like the mandibles, at the side of that aper- 
ture (the mouth), but decidedly behind it, turning their extremities more or 
less forwards, precisely as do the maxillae in other Copepoda.’’? While this may 
be true for the other Poecilostomous copepods, it obviously does not apply to the 
Clausidiidae, as can be seen at once by an examination of Sars’ figures for the 
oral area in both Hemicyclops purpureus and Hippomolgus furcifer (pl. lxxxi, 
Ixxxii). My own figure for the oral area of Hemicyclops australis (fig. 21), 
described below, agrees closely in the arrangement of the parts with those given 
by Sars, as does also the figure of Goidelia given by Embleton (1901, pl. 22, fie. 
10). Sars’ figures differ from those of Embleton and myself only in having the 
maxillule attached to the base of the mandible. 
As mentioned above, Sars admits the ‘‘maxilla-like appearance’’ of what 
he regards as the ‘‘palp or exopodite’’ of ‘‘the foremost pair of limbs’’ and 
points out its resemblance to that appendage in some of the Cyclopidae. The best 
answer to this is supplied by Sars himself in his figure for Hippomolgus furcifer 
(pl. Ixxxii, m). Here, according to his interpretation, we see a maxillule with 
a palp attached basally. In the Cyclopidae (cf. Sars, pl. xii-xvi, xliii, xlviii, and 
1) the palp is always attached to the distal portion of this appendage. 
Gurney (1927, p. 464) has discussed this question and concludes that ‘‘neither 
the structure nor the position of these appendages is inconsistent with their inter- 
pretation as mandibles.’’ While I share the hesitation expressed by Dr. Gurney 
in differing from ‘‘an authority of such eminence and accuracy as Prof.Sars,’’ it 
would certainly appear that Sars has drawn the mandible and maxillule together 
as a single appendage. Even if these two appendages were really parts of the 
same appendage it would seem more reasonable to interpret that appendage as the 
mandible, with a proximally inserted palp, as has been done by Wilson (1932a) 
and Light and Hartman (1937), As Embleton (loc. cit.) has shown in Goidelia it 
is the maxillule which has undergone the greatest reduction. 
