Vol. 57.] PENDLESIDE GEOTJP AT PENDLE HILL, ETC. 399 



groups of exceedingly minute, highly refractive bodies of no very 

 definite shape, but uniform in size, having a diameter of O'OOl mm. : 

 they are most probably only an expression of the mineralization. 



The finer-grained, light-coloured chert resembles in external ap- 

 pearance some of the cherts of the Mountain Limestone; in sectiou 

 it seems to represent the fine-grained grey limestone of Pendle. 



Up to this point, if we except the coarse-grained chert, we have 

 described no rock from the Pendleside Limestone which could not 

 be exemplified in the Mountain Limestone. The richly foraminiferal 

 limestones, for example, are exceedingly abundant in the darker 

 upper beds of the massive Limestone Series, wherever they have 

 been examined. Eoraminifera are generally present, though not 

 universally, and never so abundantly in the white limestones such 

 as those of Clitheroe, Cracoe, Millersdale, Dovedale, etc. But at 

 Chatburn, in the. dark well-bedded limestones with thin shale- 

 partings, below the white Clitheroe Limestone, they are again 

 common, and in good preservation. 



Again with regard to the dolomitized limestone, this, too, is found 

 in great bulk in certain regions of the Mountain-Limestone area as 

 an alteration -product of the latter, at Masson Hill, Matlock ; 

 Harbro' Eocks, near Brassington (Derbyshire), and elsewhere ; but in 

 this case it would nearly always be possible to discriminate between 

 the two in hand-specimens. The Pendle rock is harder-looking, 

 more crystalline and gritty in appearance than the other, and less 

 suggestive of a ' dunstone,' the local name for the magnesian form 

 of the Mountain Limestone in Derbyshire. 



In the area that we have examined, we are not aware of any 

 rock with sponge-patches resembling No. 319; but the grey fine- 

 grained limestone with sponge-remains could be matched from many 

 localities. One of the best sponge-limestones that we have yet found 

 outside the Pendle rocks is a 3-foot bed near the base of Park Head 

 Quarry, north of Lothersdale ; it is wholly composed of spicules 

 of calcite lying in a fine grey matrix. 



There is, however, on Pendleside, at difierent horizons in the 

 limestone series, a rock which we are disposed to regard as typical of 

 the horizon of the Pendleside Limestone Group, that is, of the zone 

 of Posidonomya Becheri, Posidoniella Icevis, etc., not only on Pendle 

 Hill itself, but in all other parts of the area over which we have 

 traced the zone. 



The Black Limestones. 



These rocks are usually hard and black, very compact and close- 

 grained, and exhibit a tendency to break with a subconchoidal fracture. 

 Such is their condition at the base of the limestones at Hook Cliff", 

 also at the top, and at intermediate points both above and below the 

 grey limestones. The groundmass is fine granular calcite, stained 

 ^rowu ; minute vegetable particles are nearly always visible in thin 

 sections, and in the harder forms, sections of small goniatites and 

 entomostraca. 



