68 
XI. 
On Fossil Fish. 
By W. Sanders, F.R.8., F.G.S. 
Mead at the Sectional Meeting, December 7th, 1870. 
The President, Mr W. Sanders, F.R.S. resumed the subject of Fossil 
Fishes. After reminding the Members of what he had stated respecting the 
Placoid division of fishes, he described the characters of the Ganoid division. 
This contains two sub-orders : first, the Placo-ganoid, so named on account 
of the large broad plates with which the head and forepart of the body are 
covered. The two families of the sub-order have heterocercal tails, and 
retain the notochord. The first of these is illustrated by the Pterichthys 
and Cephalaspis, and is not known later than the Old Eed Sandstone. 
The second sub-order, the Lepido-ganoid, in cludesfishes which have the 
whole body covered with shining enamelled scales. Some of these have an 
imbricate arrangement of the scales like that of the tiles on a house. They 
are chiefly heterocercal and belong to palseozoic strata. The Holoptychius 
is an example of this group. 
The remainder have scales of a rhombic form arranged very symmetri- 
cally. They are divided into nine families, of which the greater number 
are heterocercal and retain the notochord. The palaeozoic formations 
furnish remains of these, as the Dipterus, Amblypterus, and Megaliehthys. 
A smaller number are homocercal and these are found in Mesozoic strata. 
The Dapedius from the lias and the Pycnodus of the oolites, are good 
illustrative examples. 
Dr. S. Martyn then exhibited and described the scale of Holoptychius 
found by him in the Old Eed Sandstone at Portishead. He also shewed a 
specimen of Trap Rock from Worle Hill, and some large crystals of 
Celestine, or Sulphate of Strontian, from Wickwar. 
ZOOLOGICAL SECTION. 
No Meetings have been held in this Section. 
BOTANICAL SECTION. 
The Botanical Section has been occupied during its monthly evening- 
Meetings in preparing and mounting specimens for the Herbarium. 
