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PROCEEDINGS 1841 — 1848. 
Placoidians or Ganoidians, and the former specimens consist of either 
teeth or dorsal spines. Of these fine specimens of Gyracanthus 
formosus and Pleuracanthus planus have been found at Middleton 
and Adwalton ; Ctenacanthus brevis and Orthocanthus cylindricus in 
the stone coal at Adwalton ; a species of Helodus and Ctenoptychius 
pectenatus at Middleton ; and a unique specimen of Ctenodus cristatus 
upon a piece of coal from Tong, preserved in the Museum of the 
Leeds Philosophical Society. Teeth of Diplodus and Hybodus also 
occur at Middleton, and Agassiz enumerates Petalodus acuminatus 
from Leeds, and Carcharopsis prototypus, which Mr. Denny had not 
been able to trace. Of the ganoids, specimens of the genus Megalicli- 
thys appeared to have been extensively distributed through the coal- 
fields of Great Britain, more especially in the cannel or stone coal ; 
the first examples, as well as the most celebrated, being the nearly 
perfect head and portion of the body of Megalichthys hibberti, from 
Low Moor, deposited in the Museum at the Leeds Philosophical 
Society in 1823. Since that period, numerous scales and teeth have 
been detected at Middleton and Adwalton, from the latter locality, 
several large teeth two inches in length have been obtained by Mr, 
Drabble, of Leeds, who was informed by one of the pitmen that a 
large mass of scales, in length equal to one of the corves, had been 
brought up and broken to fragments at the pit's mouth . Several 
small jaws have also been obtained from the fish coal at Middleton, 
but the species to which the belong has not been determined. Numbers 
of small teeth have been obtained in the small coal at Stanley, Newton, 
and Overton, associated with coprolites ; also at Rotliwell Haigh, and 
in the roof of the better bed coal at Low Moor. Scales of Acanthodes 
and Holoptychius are not uncommon in the Middleton fish coal. 
Agassiz also mentions the species of Platysomus, and Diplopteris as 
also occurring, but where he could not ascertain. The last fish he 
named was Coelacanthus Phillipsii, of which the tail was found in the 
centre of a baum pot near Halifax, and is now in the Museum of the 
Philosophical Society of that town. Mr. Denny then proceeds to 
enumerate the species of fossil mollusca which have been found in the 
West Riding, including those commonly known from the marine beds 
of Halifax, and the fresh-water iron-stone containing unios. He 
