
NICHOLLS—COPEPODA FROM SOUTH AUSTRALIA 15 
GNATHOSTOMA. 
Famity OITHONIDAE Sars. 1913. 
Genus OrrHona Baird 1843. 
Sars, 1913, p. 4; Rosendorn, 1917. 
OrrHona NANA Giesbrecht 1892. 
Sars (19138, p. 5) suggests that this species should constitute the type of a 
new genus, Oithonina. This was not accepted by Rosendorn (1917) but Wilson 
(1932) uses Sars’ generic name for this species. I have followed Rosendorn, who 
regards nana. as the type of a group of species within the genus Orthona. 
Oceurrence. III, several females (0:52 - 0-72 mm.). 
Distribution. Widely distributed in the warmer regions, also found in the 
North Sea. The species has not, apparently, previously been recorded from Aus- 
tralian waters. 
OITHONA ATTENUATA Farran 1913. 
Occurrence. ITI, several females (0°50 mm.). 
Distribution. Chiefly Indo-pacific; recorded also from the Atlantic (Rosen- 
dorn). This species has previously been recorded from Australian coastal waters 
by Farran (1986). 
SIPHONOSTOMA. 
The bulk of this collection comprises chiefly those copepods peculiarly adapted 
for a semi-parasitic existence, for which they are provided with suctorial mouth 
parts. This interesting group has been divided by Sars into a number of families, 
all but one of which are represented here. Their more important distinguishing 
characters ean again best be summarized in the form of a key: 
Key To THE FAMILIES. 
1. Second antenna non-prehensile se ie aca 7 3 
Second antenna strongly prehensile at io .. CANCERILLIDAE Sars 1915. 
2. Fourth legs present - = or +4 3. 
Fourth legs absent “e || ARTorRoGIDAR Sars 1915. 
3. Body expanded, with well developed epimera; genital segment widened anteriorly; fifth legs 
reduced to a knob-like process; fourth endopod usually reduced or absent (in a few cases 
normal) .. DYSPONTIIDAE Sars 1915, 
Body more or less slender, usually without epimera; "genital segment only slightly widened 
anteriorly ; fifth legs 2-segmented, though penximal segment not wea: clearly defined; 
fourth endopod always well developed 
4. Sensory filament of first antenna on terminal seicintit mandible ated vats 
MyzopontTiipak Sars 1915. 
Sensory filament of first antenna sub-terminal; mandible palp present Fem 
5. Second antenna as long as first, its exopod as long as the third segment; siphon reaching at 
least to genital segment, usually to caudal rami... ACONTIOPHORIDAE Sars 1915. 
Second antenna much shorter than first, its exopod shorter than the third segment; siphon 
much shorter, sometimes absent Abe ASTEROCHERIDAE Giesbrecht 1899, sens. str. 
As will be seen, the Dyspontiidae are somewhat difficult to define as a family, 
and to separate from the others. Hansen (1923, p. 2) retains Giesbrecht’s Aste- 
rocheridae in its widest sense and disavrees with Sars’ division of that. family into 
smaller families, With the possible exception of the Dyspontiidae it appears that 
