
NICHOLLS—COPEPODA FROM SOUTH AUSTRALIA 4] 
him are probably sexual, as in the difference in the genital segment, or only of 
specific value, as in the armature of the swimming legs and shape of the fifth 
leg. Probably of generic value is the shape of the body; in Artotrogus it is 
always sub-cireular, with the urosome scarcely, if at all, projecting beyond the 
epimeral plates of the thorax; in Dystrogus the body is ovoid and the posterior 
segments of the urosome project well beyond the thoracic epimera. 
Sars (op. cit., p. 184) suggests that the shape of the female of Dystrogus 
when known may prove to resemble that of Artotrogus, implying that the differ- 
ence in shape is sexual. This is not borne out by the male of Artotrogus found 
here, which is sub-circular like the female, whereas if Sars’ implication were cor- 
rect it might be expected more to resemble Dystrogus in shape. 
Genus Artotrogus Boeck. 
Boeek, 1859; Giesbrecht, 1899, pp. 92, 111; Sars, 1915, p. 182. 
It would appear that G. M. Thomson followed Brady (1880, p. 59), who 
quite unjustifiably regarded Asterocheres, Ascomyzon and Artotrogus as synoy- 
mous. Brady’s chief reason for choosing the latter name for the genus was that 
it was ‘‘less objectionable’ than Asterocheres and has priority over Ascomyzon. 
Whereas the two former are synonymous, Artotrogus is distinct. Giesbrecht 
(1899, p. 118) includes a list of synonyms and disposes of those species wrongly 
assigned to this genus up to the time when he wrote. The following species have 
since been added: brevicaudatus Brady, 1899; gigas and sphaericus Brady, 1910; 
proximus T. Scott, 1912; and australis Wilson, 1923. 
Of the first of these Brady (loc. cit. p. 49) states that ‘‘The mouth organs 
and swimming feet present no distinctive characters’’ from which we can only 
assume that in these features the species agrees with Brady’s diagnosis for the 
genus given in 1880 (p. 59). Here it is evident that he has overlooked the absence 
of the fourth leg in Boeck’s species orbicularis, which is a true Artotrogus. We 
must, therefore, assume that brevicaudatus has a normal fourth leg, with three- 
segmented rami. From the figure of the whole animal (pl. xiii, fig. 22), showing 
well developed epimera, and that of the urosome (fig. 26) showing the genital 
segment widened anteriorly, it is clearly a member of the Dyspontiidae. Be- 
yond this one cannot go with any degree of certainty, for while it would ap- 
pear to be either Cribropontius or Sestropontius, the shape of the body is much 
more like that of Cryptopontius. The structure and size of the siphon also indi- 
cate this genus as does the claw of the maxilla, but inclusion in this genus re- 
quires that the fourth endopod should be absent. It is clear, however, that it 
does not belong to the Artotrogidae. 
It is difficult to determine whether Brady’s species gigas and sphaericus 
belong to Artotrogus or not. In spite of the pronounced sub-cireular outline of 
the body, I am inclined to doubt that they should be included. It is clear that 
sphaericus is a female, and gigas must be presumed to be so, since the genital seg- 
ment does not show the distinctive male characters. The latter species is inade- 
quately described and figured, but in both this and sphaericus the urosome is too 
long, has too many segments, and the genital segment lacks the distinctive pos- 
tero-lateral extensions found in orbicularis and australis. Further, in sphaericus 
the maxilla has the distal portion of the end claw distinct, and the whole claw 
is only slightly curved distally, whereas in orbicularis it is strongly eurved and 
undivided. In both orbicularis and australis the siphon reaches the base of the 
maxillipeds, whereas in Brady’s species it does not, but this may be of only minor 
importance. Brady’s species Dystrogus uncinatus might have been accepted as 
an Artotrogus, but for his statement concerning the fourth legs, which excludes 
it from both this genus and from Dystrogus. 
