416 REPORT—1905 
to, but specifically distinct from, the existing African species.’ Until we have 
some proof of the contrary, we are justified in regarding the Polypteridz as having 
arisen in Africa from fresh-water ancestors, themselves derived from early Mesozoic 
types which are entirely hypothetical. 
THe LeprpostRENIDS.—Protopterus in Africa and Lepidosiren in South 
America are specialised modifications of the Ceratodontide, still represented by 
one species in Australia, which have left remains in Triassic, Rhetic, Jurassic, and 
Cretaceous rocks of Europe, North America, Patagonia, North and South Africa, 
India, and Australia. The distribution of the Ceratodontide has therefore been, 
at different periods at least, a world-wide one, and we should feel justified in 
assuming the living representatives of the Lepidosirenide to have been evolved out 
of this family independently in Africa and in South America. On the other 
hand, in view of the old age of the group, there is no reason why the Lepidostrenide 
should not have passed from one of the present continents into the other when 
they were connected by land. As Protopterus is a less specialised type than 
Lepidosiren, the probabilities would then be that the former originated in Africa. 
Mr. Lydekker, in his ‘ Geographical History of Mammals,’ states his opinion that 
Lepidosiren reached its present habitat by way of Africa. The mode of life of these 
fishes renders them less dependent on hydrographical systems, and the distribution 
of the species, which cannot yet be traced ina satisfactory manner, is evidently very 
different from that of other groups. In this case, again, Mr. Moore has appealed 
to Protopterus as probably representing, with Polypterus and most of the Cichiida, 
the ‘now scattered piscian portion of the halolimnic fauna’ of Tanganyika. He, 
however, omits to mention that this fish is not known to occur in the lake itself, 
but is only reported to be found in some marshes in its vicinity, the species being 
the same as that which extends northwards to the White Nile; it should there- 
fore not be included at all among the inhabitants of Lake Tanganyika, 
Tur Mormyrip®.—This extraordinary group, of which so many new and 
remarkable types have been discovered within the last few years, especially in 
the Congo, is peculiar to the fresh waters of Tropical Africa and the Nile. Its 
morphology shows it to be highly specialised from some very lowly Teleostean 
ancestor. This I believed to be found in the Albulide, a family already repre- 
sented in Cretaceous seas, and of which one species still occurs on the West 
Coast of Africa. But Dr. Ridewood, who has recently made a much more careful 
study of the cranial characters of the two families, is unable to support the 
suggestion of a direct descent from the Albulide, It nevertheless remains 
probable that the Mormyride were derived from forms more closely allied to the 
known Albulide than to any other family with which we are acquainted, and 
which no doubt lived in Cretaceous seas; and we may therefore assume that 
the Mormyride originated in Africa, and were evolved out of Cretaceous marine 
ancestors. 
Tue Noroprertp#.—This is another eccentric family, having many points in 
common with the Mormyride and with the North American Hyodontide. It is 
represented by five species, three of which live in the Indo-Malay region and two 
in Tropical Africa, Its derivation is still a mystery. The fact that its most 
specialised form (Xenomystus) is African, and that a species differing but little 
from the living Notopterus occurs in fresh-water deposits in Sumatra, which 
are regarded by some geologists as of Middle Eocene age—although, as stated 
further on @ propos of the Cyprinide, there is reason for regarding them as 
Miocene, or even later—justifies us in believing, until further palzontological 
evidence be available, that the African forms are immigrants from the East. 
THE OsTEOGLOssIDa.—An archaic type of Teleosteans, now represented by 
two genera in South America, by one in Australia and the Malay Archipelago, 
and by a fourth in Tropical Africa and the Nile. Excellently preserved fossils 
from the Middle Eocene of Wyoming (Dapedoglossus) are most nearly allied 
to, but more generalised than, the Australian-Malay genus; whilst the less 
