He observes, "The occurrence of Indian forms on the West Coast of Africa, such as _Periophthalmus_, _Psettus_, _Mastacembelus_, is of the highest interest, and an almost new fact in our knowledge of the geographical distribution of fishes." _Ophiocephalus_, again, is a truly Indian genus, there being no less than twenty-five species,[145] all from the fresh waters of the East Indies.

Yet Dr.Guenther informs me that there is a species in the Upper Nile and in West Africa.
The acanthopterygian family (_Labyrinthici_) contains nine freshwater genera, and these are distributed between the East Indies and South and Central Africa.
The Carp fishes (Cyprinoids) are found in India, Africa, and Madagascar, but there are none in South America.
Thus existing fresh-water fishes point to an immediate connexion between Africa and India, harmonizing with what we learn from Miocene mammalian remains.
On the other hand, the Characinidae (a family of the physostomous fishes) are found in Africa and South America, and not in India, and even its component groups are so distributed,--namely, the _Tetragonopterina_[146] and the _Hydrocyonina_.[147] Again, we have similar phenomena in that almost exclusively fresh-water group the Siluroids.
Thus the genera _Clarias_[148] and _Heterobranchus_[149] are found {147} both in Africa and the East Indies.

_Plotosus_ is found in Africa, India, and Australia, and the species _P.

anguillaris_[150] has been brought from both China and Moreton Bay.

Here, therefore, we have the same species in two distinct geographical regions.