HOLOPTYCHIOID FISHES. 



67 



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cycloid, and in having a more 

 continuous and smooth layer of 

 ganoin, are the Osteolepidse, e. g. 

 Osteolepis macrolepidotus (189, 

 and fig. 88), a fish whose re- 

 mains occur in the Lower Old 

 Red Sandstone of Scotland, and 

 Megalichthys hibberti, 190, a 

 much larger fish from the Coal 

 Measures of Great Britain. The 

 vertebral column has ring-like 

 centra in the caudal region ; the 

 vertebral axis of the tail is slightly 

 up tilted, the teeth are conical, 

 with the wall only slightly 

 infolded at the base. 



The four restorations alluded 

 to in the preceding paragraphs, 

 and several others exhibited in 

 Wall-cases o—7, have been con- 

 structed after critical examination 

 of the remains of the fishes in 

 the Geological Department of 

 the Museum, and the published 

 figures of other specimens, with 

 a view to enabling the public 

 visiting this Gallery to form some 

 idea of what the fishes probably 

 looked like in the ages long ago 

 in which they lived. The size of 

 the fish, the form of the body, 

 whether rounded or flattened, the 

 shape of the various fins, their 

 positions on the body, the outline 

 of the tail, the characters and 

 arrangement of the scales and 

 head-plates — these are details 

 which may be gathered from the 



Osteo- 

 lepis. 



r2 



