ROCKS OF SOUTH DEVON. 505 



the limestone, which abounds in Alveolites vermicular is, E. & H., 

 appear to be intimately mixed with volcanic matter, so as to be, 

 in Sandberger's words, either a ' Kalk-Schalstein ' or Schalstein- 

 Kalk. A similar intimate blending of material appears to take 

 place at Factory-hill quarry, near Harbertonford." 



In a note on the site of a Starfish (named by Dr. H. Woodward, 

 Heliantliaster JUiciformis), Mr. Champei-nowne mentioned the low 

 northerly dip of the Harbertonford limestone, the occurrence, at 

 Eoster Bridge, of numerous " large Spirifers and other fossils," and 

 the predominent cleavage of the limestone *. 



At the Lion Brewery, Totnes, a boring was made to a depth of 

 139 feet in blue slate rock, under blue limestone only 2 ft. 6 in. 

 thick. 



From the above observations it is evident that an extraordinary 

 uniformity in conditions is manifested by the deposits immediately 

 preceding the volcanic outbursts, and that the volcanic materials 

 were poured out upon a muddy bottom whereon masses of shells and 

 corals were here and there accumulating. 



But, as by fossil and stratigraphical evidence, the position of the 

 limestone patches is proved to coincide with the Eifelian limestone, 

 we are at once supplied with a reliable date for the commencement 

 of this phase of volcanic activity, namely the later stages of the 

 Eifelian deposition. This is borne out by the absence of volcanic 

 materials in the Lower-Devonian and Eifelian-slate areas. 



The Ashprington series may represent continuous or intermittent 

 vulcanicity up to the middle of the Erasnian ; but, as there are no 

 newer sedimentary beds above it, no measure of its duration is 

 furnished in the Ashprington area. 



The numerous evidences of volcanic activity outside the Ash- 

 prington area are so distributed as to suggest local centres of erup- 

 tion ; thus the aphanites and tuffs of Saltern Cove and Goodrington 

 obscure the relations of the Middle and Upper Devonian, vulca- 

 nicity having there begun during a late stage in the accumulation 

 of the Middle-Devonian Limestone. Again a volcanic area north of 

 Waddeton complicates the relations of the Middle-Devonian lime- 

 stones of Yalberton and Crabb's Park and D pper-Devonian slates, 

 even suggesting partial volcanic activity near Waddeton as early as 

 the commencement of the Ashprington series. 



It is instructive to find a great development of Middle-Devonian 

 limestone on the immediate borders of the volcanic materials, north 

 of Stoke-Gabriel, as it is thereby demonstratively proved that the 

 accumulation of the limestone took place contemporaneously with 

 the Ashprington volcanic outbursts. This is further proved by the 

 occurrence of detached masses of the Berry-Pomeroy limestones in 

 direct contact with the volcanic series near True Street, east of 

 Totnes. 



IS ear Yalberton volcanic materials appear to rest on the lime- 

 stone ; but when we consider that these impersistently associated 



* Geol. Mag. 1874, p. 5. 



