Geology of the South-east of Devonshire. 469 



composed of their uninjured shells at Chudleigh, Chercombe Bridge, Bradley, and Plymouth ; again, the 

 habits of the CalceolcB are made very evident by the position in which they are found, being inva- 

 riably in the thin partings of shale which separate the lower beds of sedimentary limestone. These 

 calcareous flagstones probably soon became solid compact strata, to which fucoids attached themselves, 

 and among which the CalceolcB lived. 



The researches of fossil zoologists have hitherto been principally engaged with the forms which the 

 calcareous groups of South Devon have afforded ; the slate system not having as yet received much 

 illustration ; whenever this shall be done it will be found that the prevalence of certain generic forms, 

 and even a total change in species, are unsafe guides as to relative age ; that though the shells which 

 lived about the coral reefs of South Devon, resemble to a considerable extent such as occur in the 

 mountain limestone tracts of other parts of England, yet that the slates of South Devon aflPord fossils 

 which suggest comparisons with those from districts described by Mr. Murchison : such and very many 

 other conditions must be taken into account before organic remains can be made the framework of an 

 order of superposition for the older rocks. 



The few following species, together with many not yet made known or described, will be readily 

 found in the slates about Ogwell : — 



Fucoids. 



Turbinolopsis celtica, Lamx. Expos. Method.* 

 Cyathophylla. 



Fenestella antiqua, Lons. Silur. Syst. 

 Pieurodyctium problematicum. Gold. Pet. Germ. 

 Cyathocrinites nodulosus, Phil. Pal. Foss. 

 Crinoidal stems. 



Spirifer speciosus, var. alatus, V. Buch, Mem. 

 Soc. Geol. France. 



aperturatus (Terebrat.), Schloth. Petref. 



Strygocephalus ? (undescribed species). 



Orthis compressa, Sow. Silur. Syst. 



arachnoidea,P/«7. Geol. York.S^ Pal. Foss. 



Orthis sordida (Leptaena), Sow. Geol. Trans. 



Leptaena depressa, Dalm., His. Lethcca Suecica. 



Modiola scalaris, Phil. Pal. Foss. 



Trochus Bouei, Stein, n. s. 



Orthocerata. 



Calymene accipitrina, Munster, Bdtrdge. 



granulata, Munster, id. 



lasvis, Munster, id. 



Sternbergii, Munster, id. 



Asaphus granuliferus, Phil. Geol. York. ^ Pal. 



Foss. 

 Olenus punctatus, Stein.Mem. Soc. Geol. France. 



§ 3. Limestone of Yalberton, ^c. — The small subordinate masses of limestone in- 

 dicated on the map are usually thin-bedded, but they occur in very distinct layers, 

 are hard, sonorous, and very dark-coloured. They are also valuable, as they yield 

 large slabs, and burn into a good lime, of which much is employed in agriculture 

 throughout South Devon : organic remains but seldom occur ; I have seen only 

 Stromatopora concentrica or polymorpha. 



§ 4. Lower Limestone of Ashburton. — This great calcareous band of limestone 

 closely resembles the foregoing in character and appearance ; it has also much car- 

 bonaceous matter in seams, in which respect it is very like the limestone of Bunker's 

 Hill, near Totness ; and in both cases the vegetable matter seems due to marine rather 

 than to terrestrial vegetation, as the only impressions I have found are those of 

 fucoids. Fossil shells (Brachiopoda) and corals (Cyathophylla) are abundant, but 

 the close compact structure of the rock renders it impossible to obtain detached 



* Exposition Methodique ; for the other works referred to, see the titles in the notes to p. 466. 

 VOL. VI. SECOND SERIES. 3 P 



