Cosmo Johns: Lower Carboniferous Rocks of Mill Gill. 273 



distance the.section is obscured owing to the number of boulders 

 washed down from higher levels. During the visit of the York- 

 shire Geological Society the occurrence of limestone boulders 

 with Saccammina carteri, in the drift, had been noticed by Prof. 

 P. F. Kendall. These became more numerous as Mill Gill was 

 ascended, and the parent bed was found at a point about 25 feet 

 below the top of the Great Scar Limestone. The occurrence of 

 this particular fossil is noteworthy for it has been recorded 

 by Mr. Smith from the Acre Limestone of Lowick ; a much 

 higher level than that now recorded from Mill Gill. It is known, 

 however, that it occurs at several horizons in the Lower Car- 

 boniferous Rock, and as its range is from the Ordovician to the 

 present time, it is an interesting example of a remarkably 

 stable and persistent species. Succeeding the Saccammina 

 bed we have well-bedded grey and black limestones with oc- 

 casional shale partings, and corresponding to similar beds found 

 in the other Yorkshire Dales at the top of the Great Scar 

 Limestone. Corals are not uncommon, Lithostrotion martini 

 Syringopora sp. and occasional specimens of Cyathaxonia, the 

 specific identity of which has not 3/et been determined. 



The top of the Great Scar is a massive limestone with small 

 ' knolls ' which stand up in domes or ridges, around and over 

 which the black shales shortly to be described were laid down. 

 The resemblance of these miniature ' knolls ' to those described 

 by Mr. Lamplugh from the Isle of Man was most striking, and 

 the occurrence of Posidonomya becheri in abundance in the 

 shales which immediately succeed, strongly suggests identity of 

 level. In both areas there is an intimate relation between the 

 Cyathaxonia limestones, the knolls, and the Posidonomya becheri 

 beds. Several specimens of Trilobites were obtained from the 

 black shales. Among the brachiopods that occur in these 

 shales are : — 



Productus setosus Amboccelin sp. nov. 



elegans Spiriter trigonalis 



granulosus ,, triangularis 



undatus Pugnax cf. pugnus 



Rhipidomella michelin Orthotetes sp. 



Chonetes sp. 



It is interesting to compare this list with that recorded by 

 Dr. Wheelton Hind (Brit. Assn. Report, 1903) , from a higher level 

 in these same shales in which, in addition to the brachiopod 

 fauna, such forms as Ctenodonta Icevirostris and Stroboceras 



1910 July I 



