336 J. "W. DAYIS ON" THE GENUS PLEUEACAlTTHirS, AGASS. 



EXPLANATION OF PLATE XII. 



Fig. 1. Spine of Fleuracanthus tenuis, Davis, nat. size. 



2. Spine of Pleuracanthus pulchellus, Davis, twice nat. size. 



3. Spine of Pleuracanthus altemidentatus, Davis, nat. size. 



4. Spine of Pleuracanthus alatus, Davis, nafc. size. 



5. Spine of Pleuracanthus rohustus, Davis, nat. size. 



6. Spine of Pleuracanthus Wardi, Davis, nat. size. 



7. Spine of Pleuracanthus detiticulattts, Davis, nat. size. 



DiscirssioH-. 



The President stated that in the southern division of Yorkshire 

 fish-remains are much more common than is usually supposed. 



Dr. Dfncan remarked upon the variability of spines in fishes. 

 He welcomed the reduction in the number of genera, but was not 

 prepared to accept Mr. Davis's views on the affinities of these fish, 

 especially in the absence of all Teleosteans from the Secondary for- 

 mations. 



The Atjthoe stated that many tons of fossil fish-remains must 

 have been destroyed before the interest of the coal band was dis- 

 covered. In reply to Dr. Duncan, he deprecated the acceptance of 

 negative evidence as to the absence of Teleostean forms in Mesozoic 

 times. He argued that both Coelacanthus and Pleuracanthus were 

 probably freshwater fishes, the former possessed of an air-bladder. 



