TRANSACTIONS OF SECTION D. ~ 415 
ACANTHOPTERYGII. 39. Pleuronectide, 2, 2. 
30. Centrarchide, 1, 3. 40, Gobiide, 2, 31. 
31. Nandide, 1, 1. ‘41. Blenniide, 3, 3. 
32. Serranide, 6, 8. 
33. Sciznide, 1, 1. OPISTHOMI. 
34. Pristipomatide, 2, 2, | 42. Mastacembelide, 1, 23. 
35. Sparidse, 1, 1. fe 
36. Scorpidide, 1, 3. 3 
37. Osphromenide, 1, 1, Ee aioe 
38. Cichlide, 30, 179. 43. Tetrodontide, 1, 4. 
In discussing the distribution of the fresh-water fishes it is necessary to divide 
them into four principal categories :— 
1. Those living part of the year in the sea, This category is again subdivided 
into anadromous forms, breeding in fresh water (ex. some C/upea), and catadromous 
forms, breeding in salt water (ex. Anguilla). ‘ 
_ 2. Those living normally in the sea, but of which certain colonies have become 
land-locked, or have separated themselves from the marine stock still represented 
on the neighbouring coast (ex. some Gobiide and Blenniide). 
3. Those which, although entirely confined to fresh waters, have as nearest 
allies species living in the sea, and which there is reason to regard as more or less 
recently derived from marine forms (ex. Galaviide, Tetrodontide). 
4. Those belonging to families entirely (ex. Mormyrid@, Characinide) or chiefly 
(ex. Siluride, Cyprinodontide) restricted to fresh waters. 
The forms of the first and second categories may be entirely neglected in dealing 
with the distribution of fresh-water fishes. Their range is regulated by the sea, and 
they must be dealt with in conjunction with littoral forms. Eighty-six species in 
the list of African fresh-water fishes belong to these categories. 
The third category is of secondary interest in the history of the fresh-water 
fauna; but, as in the case of Galaxias, forms referred to it may give rise to dis- 
cussion. 
It is with the members of the fourth category that we shall mainly deal in 
the portion of this Address which is devoted to the origin and mode of dispersal of 
the African fishes. 
THe Potypreripm.—This is incontestably the most remarkable family of 
African fishes. Entirely restricted to Tropical Africa and the Nile, without any 
known near allies, living or extinct, its history is one of the greatest riddles in 
ichthyology. From the evolutionary point of view, no group is of greater intcrest, 
owing to its probable relation to the Chondropterygians or Elasmobranchs, to the 
Osteolepid Crossopterygiaris, out of which the Lung-fishes seem to have been 
evolved, and to the earliest pentadactyle vertebrates, the Stegocephalous Batra- 
chians. Although generally brigaded by modern systematists with the Osteo- 
lepida in the order-Crossopterygii, it is still doubtful whether it should not rank 
as a distinct order, Cladistia of Cope, the characters which differentiate it from 
these early Teleostomes being perhaps of greater importance than those which 
separate these from the Dipneusti. Perhaps the embryological material collected 
by the lamented J. S. Budgett, who sacrificed his life in his attempt to contribute 
to the solution of this great problem, will, when thoroughly worked out under 
the direction of Professor Graham Kerr, throw fresh light on the question. But it 
is rather to the future discoveries in the field of paleontology that we must turn our 
hopes. At present we know nothing on this subject, for I need hardly remark that 
Mr. Moore’s assertion that Po/ypterus had allies in the Jurassic seas, and thus 
came to enter the lake which he regards as peopled with the remains of so ancient 
a fauna, is without any foundation, as is also his statement that Polypterid 
remains were discovered by Mr. Drummond on the north-west shore of Lake Nyassa, 
these fossils having been determined by Dr. Traquair as Palzoniscid and allied to 
if not identical with Acrolepis. We are at a loss to find an explanation for Mr, 
Moore’s statement that these fossils, ‘ according to Professor Traquair, are similar 
