506 MK. W. A. E. U8SHER ON THE DEVONIAN 



materials have since been inverted, plicated, faulted, and chemically 

 altered to a very great extent, it is not extraordinary that we are 

 unable to trace the different incursions of the tufts and ashes of the 

 successive eruptions of this ancient Krakatoa, or to distinguish the 

 necks from which they emanated. 



The Middle-Devonian limestones are frequently dolomitic, and 

 where this is the case their surface is susceptible of irregular disso- 

 lution into hollows, wherein overlying tuffs would gradually sub- 

 side. This state of things no doubt to some extent accounts for the 

 irregular indentations of the volcanic and limestone boundaries near 

 Aish and Yalberton; but near Goodrington and East-Ogwell the 

 accumulation of limestone has been distinctly interrupted by local 

 influxes of volcanic materials. Felspathic tuffs occur in the tipper- 

 Devonian slates south of Goodrington. North of Little Hempston 

 the Middle-Devonian slates (replacing limestones above the Eifelian) 

 contain tuffs and occasionally schalsteins. The limestone of 

 Dartington is partially replaced by diabase ; this is also the case 

 with the Bickington limestone. At both Bickington and Ashburton 

 the limestone is overlain by tuff's and schalsteins. The Kingsteignton 

 limestones are bounded by tuffs, schalsteins, and aphanites, which 

 appear to be inverted upon them. 



North of Broadhempston numerous patches of diabase occur in 

 Middle-Devonian slates. Between Newton- Abbot and Woodland 

 there are also an infinite number of diabase and melaphyr patches in 

 the Upper-Devonian slates. The Babbacombe limestone, which is of 

 the same age as that of Dartington and Marldou, is plicated with a 

 mass of diabase, occasionally associated with purple igneous rocks 

 identical with peroxidated materials in the Ashprington series ; in 

 the Babbacombe cliff and beach-reefs masses of diabase, in some 

 places coarsely porphyritic, occur. 



Spilosite is frequently noticeable in the Upper-Devonian slates at 

 contact with the diabase, particularly north-west of Chircombe 

 Bridge. This type of contact-metamorphism has been recognized in 

 the Middle-Devonian slates of Babbacombe by Dr. Kayser. 



§ yil. Upper Devonian. 



Prior to 1887, Mr. Lee's find of the Biidesheim fauna at Saltern 

 Cove, and of the Goniatite-limestones at Lower Dunscombe, and the 

 Acervularia-limestone of Eamsleigh, were the only proved occur- 

 rences of Upi^er-Devonian rocks in this district. Li 1887 1 dis- 

 covered inliers of Upper-Devonian slate at and near Livaton in the 

 Culm-measure area south of Bovey-Tracey, and also near Lew ell in the 

 Chudleigh area. The discovery of CJymenia Icevir/aia, in irregular 

 grey and greenish slates, near Lewell by M. Tschernyschew, and the 

 identification by Kayser of the red slates beneath them, with Posido- 

 nomya venusta and Entontis serratostriata, as the Cypridinen-Schiefer 

 of Nassau and the Harz, supplied a clue to past and future work, as 

 1 had identified exactly similar slates in Kingsteignton Railway- cutting 

 and in Anstey's Small Cove, Torquay, and had discovered both these 



