58 



J. BTJCKMAtf ON AMMONITES PEOM THE 



concerned, on the same slab will be representatives of several of the 

 zonal divisions of different authors. This may be judged from the 

 fact that on the surface of slabs from this bed other Ammonites 

 besides the following have been noted. 



Ammonites jurertsis, Ziet. 



Sowerbyi, Miller. 



Humphriesianus, Sow, 



Braikenridgii, Sow. 



linguiferus, B Orb. 



Sauzei, IX Orb. 



Ammonites Gervillii, Sc 



■ Brongniarti, Sow. 



■ subradiatus, Sow. 



■ lgeviusculus, Sow.. 



discus, Sow. 



Parkinsoni, Sow. 



Some species prevail to such an extent that hundreds of indivi- 

 duals may be found in a square yard of the bed, one species prevail- 

 ing at one quarry, and another at other quarries. 



So numerous are individuals in some quarries, and so varied do 

 they seem, that it is hardly possible to escape the conclusion that the 

 family must have hybridized to a considerable extent. Anyhow, 

 under such circumstances, it is exceedingly difficult to accurately 

 define species — much more so than in the Cotteswold district, where 

 it would be difficult to find more than half a dozen forms in a 

 day. 



But besides this, when we compare the Dorset and Somerset Am- 

 monites with the Gloucestershire forms, we find that the former 

 are usually sharp and well preserved, while the latter are consider- 

 ably rougher and more fragmentary. Thus it is that shells with 

 their terminations are rare in the latter county, while with us they 

 are comparatively common. 



The specimens laid before the Society are a sufficient evidence of 

 this fact ; and they are fast increasing, now that this matter is being 

 more carefully investigated, the truth being that collectors seem to 

 have vied with each other in squaring up the mouths to make them 

 neat and tidy. Many among them, indeed, would cut away all of 

 the outer chamber, preserving only the inner chambers, which, being 

 more or less filled up with carbonate of lime, were said to be alive, 

 whilst the outer one, filled up with indurated mud, was pronounced 

 to be dead, and so was removed as useless. 



But not only do we find our Dorset specimens to be much like 

 the French ones (as figured by D'Orbigny) in condition and state of 

 preservation, but the species from the two sides of the Channel are 

 almost identical : thus we have within four of the whole of D'Or- 

 bigny's figured specimens from the Inferior Oolite of France. 



But, besides this, there are several species in our own Cephalopoda- 

 bed, now admitted to be high up in the Inferior Oolite, which 

 D'Orbigny has allocated to the Lias. This, we take it, has been 

 mainly due to the fact that this bed has been confounded with the 

 ene at the base of the Inferior Oolite in Gloucestershire. 



In this list are the following : — 



Ammonites insignis, Schubl. 



variabilis, B Orb. 



Murchisonae (?), Sow. 



discoides, Ziet. 



Ammonites Grermaini, BOrb. 



jurensis, Ziet. 



cornucopia, Young 4" Bird. 



torulosus, Schubl. 



