DEVONIAN AND OLD RED SANDSTONE KYSTKM L'07 



and Stromatoporoids only occurring at intervals and never 

 being more than 3 or 4 feet thick, while tin: tliii-kness of such 

 bedded linn-stone may vary from 100 to 300 feet. Such limestones 

 are typically developed round Dartington and Little Hempstead, 

 near Totnes ; they also occur at Ashburton, at Galmpton near 

 1 ):irt mouth, at Torquay, and Babbacombe. Their most characteristic 

 fossils are: Pachypora reticulata, Favorites fibrosus, Cyathophi/lluui 

 caspitosum, Cystiphyllum vesiculo&um, Mesophyllum helianthoides, 

 and Alveolites vermicularis. 



The higher limestones are of much lighter colour and often 

 make beautiful marbles, being grey or nearly white, pinkish, or 

 grey mottled with red. They are generally massive and unstratified 

 and are frequently largely composed of Stromatoporoids, some 

 masses of which are from 3 to 4 feet across ; compound corals 

 occur as scattered and generally broken lumps, the commonest 

 being Pachypora cristata and Heliolites porosus. 



These limestones in the Plymouth and Torquay districts pass 

 up into beds which contain a mixture of Middle and Upper 

 Devonian species. These are also massive but shelly limestones, 

 the chief constituents being crinoids, small Stromatoporoids, 

 broken corals and shells. Of corals the commonest are Pachypora 

 cristata, Alveolites suborbicularis, and Phillipsastrea (Smithia) Pen- 

 gellyi. Of shells there are Stringocephalus Burtini, Rhynchonella 

 cuboides, Pentamerus brevirostris, Spirifer curvatus, Atrypa reticularis, 

 and Cyrtina heteroclita, with, less commonly, the trilobites Bronteus 

 yranulatus and Cyphaspis occellata. The fauna of this limestone has 

 been described and figured for the Palaeontographical Society by the 

 late G. F. Whidborne. The thickness of massive limestones near 

 Torquay is probably over 200 feet. 



In North Devon the Middle Devonian consists of a series of 

 grey slates and flagstones with lenticular layers of earthy limestone. 

 The lower part is sometimes called the Combe Martin Beds, hut 

 they are only the lower part of the Ilfracombe Beds and contain a 

 similar fauna ; the lower beds are rather more sandy and flaggy, 

 while the higher beds are silvery -grey slates. The whole series is 

 intensely plicated, compressed, and cleaved, the observable dips 

 being generally those of isoclinal folds dipping southward so that 

 the actual thickness of the series is nothing like so great as the 

 breadth of basset-surface would seem to indicate, and may not be 

 more than from 1000 to 2000 feet. 



Like all the other divisions of the Devonian in North Devon 

 and Somerset it occupies a continuous band or tract of country, 

 crossing Exmoor and the Brendon Hills from west to east It 

 crops out again in the Quantock Hills, and presumably it and the 



