TRANSACTIONS OF SECTION D. ALY 
satisfactorily known British Lower Eocene Brychetus appears nearer to the South 
American Arapaima. The African genus Heterotis is the most specialised form. 
The Ostcoglosside are evidently an ancient group, now in process of extinction, 
which once had a very wide distribution. The fact of the only known fossil 
tepresentatives being from North America and Europe does not seem sufficient 
evidence of the northern origin of the family, as suggested by Mr. Lydekker. 
PantTopontTidz, PHRACTOLAMID®H, CROMERIID®.—Three monotypic families 
peculiar to Aftica. The first bears a near relationship to the Osteoglosside, and 
was probably derived from them; but the two others, discovered within the last 
few years, are so aberrant and isolated among the Malacopterygians that we are 
absolutely in the dark as to their possible origin. 
Tue Cuaractnip&®.—This is one of: the larger groups of African fisties= 
with ninety-three species, referred to twenty genera, mostly from the Nile and 
Tropical Africa, as far east as the great lakes, but only very sparsely represented 
in Kast and South Africa. 
One of the most striking features of the South American fresh-water fish- 
fauna is the extraordinary number and variety of forms of the Characinide, 
unquestionably one of the most lowly aud generalised groups of exclusively 
fresh-water Teleosts. There occur in that part of the world as many as 500 
species (about two-fifths of the whole fresh-water fish-fauna), divided among 
some sixty genera. The carnivorous forms predominate, but the herbivorous or 
semi-herbivorous are also very numerous. ‘The latter would evidently compete 
with the Cyprinids, their near but more specialised relatives, which are so 
numerously represented in North America; and it isa remarkable fact that not 
a single Cyprinid is known to extend further south than Guatemala. 
Although paleontology has taught us nothing respecting the Characinids, we 
have reason to assume, from the morphological point of view, that they were the 
precursors of the Cyprinids, which, we know, were already abundantly repre- 
sented in North America and Europe in Lower Tertiary times, when the Isthmus 
of Panama was under the sea. When, in the Miocene, North and South 
America became reunited, the waters of the latter part of the world must have 
been already so fully stocked with Characinids as to prevent the southern spread 
of the Cyprinids. This is the only explanation that can be offered of the total 
absence of Cyprinids in South America, considerations of climate being of no 
ayail in view of their distribution all over Africa. If, therefore, the Characinids 
existed in profusion in South America before the Miocene period, we are justified 
in claiming for them a high antiquity, and by putting it at the Upper Cretaceous 
we need not fear going too far back. As it is admitted by most geologists that 
a continuous land communication probably existed across the Atlantic between 
South America and Africa up to the end of the Upper Cretaceous period (not, 
however, in the position designed by Dr. Ortmann, as is proved by the recent dis- 
covery of Turonian beds in the French Soudan, in Nigeria, and in Cameroon), it 
is legitimate to explain the distribution of the Characintde—Africa and Central 
and South America—by such a bridge. This explanation tallies well with the 
fact, pointing to a severance from remote times, that, although the Characinids 
of the old and new worlds show near affinity, no single genus is common to 
both. The further fact that the most generalised genera (Liythrinine) are now 
found in America points to the African forms having migrated from the West. 
When, at some time during the later part of the Cretaceous period or at the 
dawn of the Eocene, the Characinids reached Africa, and established themselves 
in the western and central waters, there were no Cyprinids to compete with 
them; but their spread to the east was soon checked by the invasion of the 
latter from the north-east; further, by the time they reached East Africa the 
bridge to Madagascar had ceased to exist. 
On the other hand it is quite true that, as pointed out by Mr. Lydekker, the 
blank in the paleontological record can scarcely be taken as a sufficient indication 
that the family Characinide has always been a southern one. 
1905, EE 
