112 REPORTS ON THE STATE OP SCIENCE. 



additional excavations at and near the critical locality known as Robin 's 

 Tump, working out the sequence of, and collecting and determining the 

 fossils yielded by, the Cambrian rocks at this part of the area. The 

 positions of these new excavations can be sufficiently identified by 

 reference to the map published with my previous Eeport. In that 

 Report x I pointed out that so far as the excavations had then been 

 carried out, ' the evidence points to the conclusion that the greenish 

 micaceous sandstone of Eobin's Tump belongs to the Lower Comley 

 Sandstone as previously defined, and that it is overlain unconformably 

 by the Conglomeratic Quarry Ridge Grit of Paradoxides age.' 

 'Further excavations between 29a and 29b are urgently required.' 

 To these further excavations my field work in 1910 was mainly devoted. 



Excavations at Robin's Tump. 

 Excavation 29, Summit of Robin's Tump. 



In order to determine the actual relations of the various strata at 

 this critical locality, I opened out a shallow trench, some 20 yards long, 

 connecting excavation 29a with 29d (see map, 1910, mentioned above) 

 and extending almost the whole length of the summit. This new trench 

 when completed gave a continuous section of the rocks concerned, and 

 is here plotted to the scale of 12 feet to the inch, or T \± (fig. 1). 



Fio. 1. — Section exposed by excavation at the top of Robin's Tump, Comley, 

 1909-10, showing unconformity between the Quarry Ridge Grits and the Lower 

 Comley Sandstone. 



*e< ■» « 

 N E. / 





f 



i **" / 7 — *Z^~3**^ j- A s.w 



Feet y 2 y* 



S } Exc.29d. 



Quarry Ridge Grits 0?^?J Lower Comley Sandstone with Calcareous Bands /////// 

 Surface of Unconformity — ' -^ Faults / 



y' 



Note. — The continuous shaded parts denote the actual excavations made. The 

 upper full line denotes the profile of the summit seen above the excavation, and the 

 detached shaded portions the positions of the natural exposures. 



Visible Evidences of the Surface of Discordant Superposition. 

 The left-hand (north-east) end represents excavation 29a. Here (as 

 pointed out in the Sheffield Report) the Quarry Ridge Grits lie discord- 



1 Brit. Assoc. Report, Sheffield, 1910. 



