Yol. 68. J SUCCESSION IN THE NOETH-WEST OF "ENGLAND. 477 



aud other calcareous fragments and their mechanical separation 

 from the sand-grains, for these grains must have been originally 

 distributed uniformlj^ throughout the deposit. It is true that a 

 ground-mass of crystalline calcite exists throughout the rock, which 

 may have been in solution while the concentration of the calcareous 

 elements took place, and may thus have facilitated the migration 

 of the fragments and the coloured impurities during the con- 

 solidation of the deposit. 



The development, then, of 'spotted' beds would seem 

 to be the result of a greater or less manifestation 

 of concretionarj^ action, depending upon the relative 

 purity of the original deposit. This concentration of 

 the material to form the spots appears to have taken 

 place during the consolidation of the deposit, and not at 

 any subsequent period; it may therefore be regarded 

 as pene-contemporan eons. 



The 'Pseudo-Breccias.' 



These are practically limited to the higher portions of the sub- 

 zone. The rock varies in appearance, from a somewhat concre- 

 tionary-looking nodular limestone to an angular breccia of which 

 the fragments measure several inches across. The structure 

 differs from that of the ' spotted ' beds in two ways ; in the first 

 place by the more rugged and angular character of the darker 

 patches when these are present, and secondly by the manner 

 in which the rock weathers. As a rule, it is composed of similar 

 fragments which cannot be differentiated into inclusions and matrix,, 

 and the mode of origin of these breccias is evidently different from 

 that of the spotted beds described above. It appears to be due to 

 weathering along definite irregular lines of strain set up in the 

 rock either during, or subsequent to, consolidation (most probably 

 the former), rather than to the separation of material by concre- 

 tionary action. In fact, the lines would appear to be analogous to 

 the spheroidal structures observed in basaltic rocks, and attributed 

 to the strain set up on cooling and consolidation. 



These beds of ' pseudo-breccia ' form the higher dip-slopes of the 

 Lower Dibunophyllum Sub-zone in all the districts. They are 

 specially well developed on Hampsfell and along the coast, in the 

 Grange and Arnside Districts.^ 



Fauna. — CyathojyJiyllum murcJiisoni occurs throughout the 

 sub-zone, and Dihunopliylliim and Carcinopliyllum also occur 

 abundantly — the latter being especially characteristic of the upper 

 portion, which also contains rare examples of Aulopliyllum cf. 

 ■pachyendotheciim. Many of the beds are rich in Lithostrotion martini 

 and L. junceum in the higher layers, especially in the liavenstone- 

 dale District. Both Alveolites etheridgi and A. capillaris are locally 

 abundant. Large Campophyllids are also characteristic of the 



1 Since this paper was read, Mr, E. E. L. Dixon has described similar 

 structures iu the limestones of South Wales ; see Q. J. G. S. yol. Ixyir 

 (1911) pp. 507-11. 



