482 PROF. E. J. GAEWOOD OX THE LOWER CARBOXIFEROtrS [DeC. I 9 12, 



that the upper boundar}- of the Melmerby-Scar Limestone some- 

 times does, and sometimes does not coincide with the base of the 

 Upper Dihunophyllum Sab-zone. The beds contain a similar fauna 

 throughout these two districts, and much the same assemblage is 

 also met with at Humphrey Head in the Grange District. Lonsdalia 

 Jloriformis and CiiatliophylJwn regium are the most characteristic 

 fossils, together with reefs of LitJiostrotion junceum, while Dipliy- 

 phi/Uwn lateseptatum \^ also present in the sub-zone in many places. 

 Froductus giganteus again is common in the Pennine area, but is 

 rare in the Shap District; and Dihunopliyllum muirheadi occurs 

 locally in the southern portion of the Shap District. 



(^ 11) The jSTodular Girvanella Band. 



This is one of the most constant horizons in the North of England, 

 and occurs at intervals, from the extreme north of jN'orthumberland 

 to Penyghent. It invariably forms the base of the Upper Dibuno- 

 2oliyllum Sub-zone, and consists of a few inches of impure nodular 

 limestone. The nodules, which average about an inch in diameter, 

 are not true concretions, but are formed of concentric coats of 

 carbonate of lime deposited round fragments of shells, crinoid- 

 stems, etc. Microscopic sections show that the deposit is probably 

 of organic origin, and is associated with more than one form of 

 algal growth. Girvanella tubes occur in many of the nodules, while 

 in others the microscopic structure is obscure. On freshly-broken 

 surfaces the nodules appear as brown spots, and exhibit a porcel- 

 lauous texture resembling Solenopora and other algal growths. 

 On weathered surfaces they stand out in relief, and their concentric 

 structure is clearly visible. In some exposures the nodules are 

 stained by hoematite. The best exposure of the band occurs on 

 the east side of Humphrey Head in the Grange District, and at 

 Tirell and Wintertarn in the Shap District. In the Pennine 

 District it is again found in the lowest Yoredale limestone, exposed 

 in Scordale Beck and High-Cup Gill.^ 



The Producfus-Gf. giganteus Band. — This band has only 

 been met with in the Shap and Pennine Districts : that is to say, 

 where the Yoredale type is developed. It is well exposed on 

 Gathorn Plain, and there forms the highest layers of the Maulds- 

 Meaburn Limestone. This band has also been found at the same 

 horizon in the Pennine escarpment. "Where present, it may be 

 taken as the upper limit of the Lonsdalia-floriformis Beds. 



(i 12) The Saccammin a-carteri Ba.nd. 



is especially well developed in the Shap District, where it occurs 

 in the Little Strickland Limestone and can be traced throughout 



1 Outside the area under description the same band occurs in the Oxford 

 Limestone in Northumberland, and in the first limestone above the massive 

 Lower Scar Limestone above Hunt Pot, Penyghent, and near Ribble Head. 



