Birge—Notes on Cladocera. 
1023 
later sketches would have shown that other differences, notably 
in the antennule, existed between the forms under comparison. 
3. Ho change was made in the situation by Herrick’s error 
of 1887. His P. bidentata 1884 remains a monotypical genus. 
4. Daday in establishing his genus Parasida overlooked Her¬ 
rick’s paper of 1884, and supposed that Pseudosida was origin¬ 
ally proposed for species having an antennule like Latonopds. 
Writing of his Parasida he says: (’05, p. 218) “Die erste 
Art dieser Gattung hat E. v. Daday unter dem Hamen Pseu¬ 
dosida szalayi 1898 aus Ceylon beschrieben.” He thus ignores 
the fact that P. bidentata Herrick 1884 is the first species and 
the type of the genus Pseudosida. Parasida , therefore, be¬ 
comes a synonym for Pseudosida and if the tridenta forms 
are regarded as belonging to a distinct genus, a new name must 
be found for it. 
5. The question of the specific name tridenta or, correctly, 
iridentata Herrick 1887 offers more difficulty; but it need not 
be discussed until the form which Herrick had before him is 
determined beyond question. If Stingelin’s species (’06) 
proves identical there is only the question whether the species 
tridentata belongs to him or to Herrick. 
Description of P. bidentata. 
Female: The general form, as seen from the side, recalls 
Sida in some respects and Latonopsis in others. The form of 
the large head especially resembles the former genus; as there 
is a rostrum which usually lies close to the valves; though as 
the head is movable the beak may be at some distance from 
them, even when the animal is alive and under no pressure. 
Compare plate LXVII, figs. 1 and 4 both drawn with camera 
lucida from living specimens, lying free on a slide without 
cover-glass. In preserved specimens the contraction of the 
powerful antennary muscles draws the head dorsad and gives 
it a wholly unnatural position and distorts the general outline. 
Daday’s figure of P. variabilis' (’05, PI. XIV, fig. 9), which 
might be drawn from my alcoholic specimens of P. bidentata, 
may be compared with the figures of living specimens in this 
