Yol. XXviii] PALiEONTOLOGY OF LANCASHIRE COAL MEASURES. 393 



Both species were described and figured in the Manchester 

 Memoirs, Yol. XLI. (1897), No. 6, by the writer. 



The type specimens are in the Manchester Museum, and 

 are registered as follows : — 



Raphistoma (?) ornata, Bacup, Rossendale. (L. 3494, 

 e coll. Bolton.) 



Naticopsis globularis, Carre Heys, Colne. (W. 467, 

 e coll. Wild.) 



Cephalopoda. 



Our knowledge of the cephalopoda of the coal measures is 

 at present of the scantiest. They are mainly restricted to 

 the Lower coal measures, if we except a very few, most of 

 which are found in the remarkable " marine band " at 

 Dukinfield. Whilst cephalopods were fairly abundant both 

 in species and numbers during the marine phase of the Car- 

 boniferous Limestone, and also of large size, they show a 

 great falling off in the succeeding Yoredale shales and Mill- 

 stone Grit series. 



A comparison of a series of cephalopod forms from the 

 whole of the Carboniferous System shows that there was, with 

 the passage from the purely marine conditions of the Carbon- 

 iferous Limestone to the later littoral and lagunal conditions 

 of the Millstone Grit and Coal measures, an equally progres- 

 sive reduction in size, numbers, and species. 



The inference seems clear that the altered conditions were 

 unfavourable to cephalopod life, and resulted in starvation. 



The occurrence of cephalopods in the Coal measures is 

 restricted to those horizons which from their fossil contents 

 indicate some return to the original marine conditions. 



This is notably the case with the shales forming* the roof 

 of the Mountain Four Feet and Bullion Seams, where most 

 of the cephalopods of the Coal Measures occur. 



14b 



