Distribution of the Plotosidae — Lanzing 
499 
Fig. 1 . Distribution of the Plotosidae. , Principal range of the Plotosidae; . . . , range of Plotosus 
anguillaris ; / / /, range of Paraploiosus albilabris. For letter symbols see footnote for Table 1. 
limit of its range is formed by the Southwest 
Asiatic Barrier (Ekman, 1953), as it has been 
found in the Red Sea and the Suez canal 
(Fowler, 1956). Although present along the 
East African coast, it does not reach Cape 
Town (Smith, 1949). It occurs in Korea 
(Mori, 1952) and Japan (Okada, 1955) as 
well as in the Society Islands; the Eastern 
Pacific Barrier (Ekman, 1953) apparently 
forms the eastern limit of its range. Plotosus 
anguillaris is not recorded from the Marshall 
and Marianas Islands (Schulz, 1953), which 
ichthyologically are more related to the Hawai- 
ian region. 
The distribution of the other plotosids, how- 
ever, is strictly limited to the Australian region. 
Of the marine plotosids only Cnidoglanis 
macrocephalus is found all along the coast of 
mainland Australia, Tasmania, and New 
Guinea; the other marine species occur only 
in the northern half of Australia and in New 
Guinea. Most of the freshwater plotosids are 
indigenous to the Leichhardtian fluvifaunula 
(see map by Whitley, 1959), although Tan- 
danus tandanus Mitchell, for instance, is con- 
fined to the Mitchellian fluvifaunula. Table 1 
shows that several freshwater plotosids are 
common to both Australia and New Guinea 
(e.g., Porochilus obbesi Weber). Other spe- 
cies are exclusively New Guinean, e.g., Neo- 
silurus gjellerupi (Weber), or Australian, e.g., 
Tandanus tandanus. Munro (1964) recently 
drew attention to the existence of differences 
between the ichthyological fauna of northern 
New Guinea (Gaimardian fluvifaunula) and 
that of southern New Guinea (Riechian fluvi- 
faunula). Apparently, some plotosids like 
Neosilurus gjellerupi and N. ater sepikensis 
(Whitley) live in the Gaimardian area, whereas 
N. brevidorsalis (Gunther) and N. ater ater 
(Perugia) are confined to the Riechian area. 
THE PRESENCE OF A DENDRITIC ORGAN 
AMONG THE PLOTOSIDAE 
Table 1 lists two groups of Plotosidae: the 
species in group A possess a dendritic organ, 
whereas this organ is lacking in the plotosids 
of group B. The species of group A occupy a 
marine or estuarine habitat, but thus far Olo- 
plotosus mariae Weber and Plotosus papuensis 
Weber have been found only in fresh water 
