548 PEOP. E. J. aAEWOOD ON THE LOWER CAEBONIEEEOUS [DeC. I912, 

 IX. SlJMMAET AND CONCLUSIONS. 



Zonal Divisions. 



The Lower Carboniferous rocks of the I^orth-Western Province 

 may be divided into a series of palseontological zones and sub-zones, 

 set forth in the table (fig. 2) on p. 452, which, with the exception of 

 the Cyrtina-carbonaria Sub-zone, have been recognized in all of the 

 districts described.^ 



In the type-districts of Shap and liavenstonedale a series 

 of palasontological horizons or ' bands ' have also been determined 

 which are of great local value ; the majority of these can be 

 traced in the other districts whenever the same horizons are 

 exposed. As examples, I may cite the CJwnetes-a'S. comoides Band 

 at the summit of the Lower Dibunopliyllum Zone ; the Camaro- 

 toechia-jrroava Band, which is found throughout the Shap and 

 Eavenstonedale Districts, and at Meathop in the Arnside District; 

 the Algal Layer, which occurs at the base of the Seminula-gregaria 

 Sub-zone, and extends throughout the type-districts, the Kendal 

 and Arnside Districts, and as far west as Plumpton in the Furness 

 District ; and the Thysanopliyllum Band, which forms a well-defined 

 horizon throughout the type-districts, under Roman Pell in the 

 Pennine District, in the Xendal District, and in the eastern portion 

 of the Grange District. On the other hand, some bands (such as 

 the Bryozoa Band, the Saccaminina-carteri'^Qjidiy and the Daviesiella- 

 llanr/oUensis Band) are limited to certain portions of the eastern 

 districts. 



Lithology. 



The sea in which the Lower Carboniferous rocks of the i^orth- 

 Western Province were deposited does not aj^pear ever to have 

 reached a great depth, the majority of the beds being evidently laid 

 down in shallow water. The period of greatest submergence oc- 

 curred during the deposition of the upper portion of the Productus- 

 cjrrugato-liemisphericus Zone and the Lower Bihunophyllum Zone, 



The lithological characters which mark the different horizons are, 

 as a rule, constant over large areas. Dolomites and porcellanous 

 cementstones are characteristic of the Athyris-glabristria Zone, 

 and locally also of the highest Yoredale limestones. This dolo- 

 mitization was penecontemporaneous, as shown by a study of the 

 dolomites in the Shap District. Occasionally, it would seem to 

 have been selective : thus Solenopora and other calcareous algae are 

 usually quite unaffected, although they are tj^pically associated 

 with dolomitic deposits. Oolites are specially characteristic of the 

 Brownber Pebble-Bed and of the beds immediately overlying it 

 in the Eastern Districts ; but thin bands of fine oolite occur also 



^ The Cyrtina-carhonaria Sub-zone cannot be clearly differentiated from the 

 overlying l^eTnatopliyUum-minus Sub-zone in the Arnside, Grrange, and Furness 

 Districts. 



