24:0 LOWER MIOCENE, ISLE OF WIGHT. [Ch. XIV. 



fig. 176, occurs a shell identified by some conchologists with a species now liv- 

 ing, P. unicolor ; also several species of Lymneus, Planorbis, and Unio. 



3. The next series, or middle freshwater and estuary marls, are distinguished by 

 the presence of Melania fasciata, Paludina lenta, and clays with Cypris ; the 

 lowest bed contains Cyrena semistriata, fig. 112, mingled with Cerithia and a 

 Ponopcea. 



4. The lower freshwater and estuary marls contain Melania costata, Sow., Melanop- 

 sis, &c. The bottom bed is carbonaceous, and called the " Black band," in which 

 Rissoa Chastelii, fig. 175, before alluded to, is common. This bed contains a 



Fig. 173. Fig. 174. Fig. 175. Fig. 176. 



Cerithium plicatum, Cerithium elegans, Eisaoa Chastelii, Nyst. Paludina lenta. 



Lam. Hempstead. Hempstead. Sp. Hempstead, Isle Hempstead Bede. 



of Wight. 



mixture of Hempstead shells with those of the underlying Upper Eocene or Bern- 

 bridge series. The mammalia, among which is Uyopotamus bovinus, differ, so far 

 as they are known, from those of the Bembridge beds. Among the plants, Pro- 

 fessor Heer has recognized four species common to the lignite of Bovey Tracey, a 

 Lower Miocene formation presently to be described : namely, Sequoia Couttsice, 

 Heer ; Andromeda reticulata, Etting ; Nymphcea Doris, Heer ; and Carpolithes 

 Webster i, Brong.* The seed-vessels of Char a medicaginula, Brong., and C. 

 helecteres are characteristic of the Hempstead beds generally. 



The Hyopotamus belongs to the hog tribe, or the same family as 

 the Anthracotheriuui, of which seven species, varying in size from the 

 hippopotamus to the wild boar, have been found in Italy and other 

 parts of Europe associated with the lignites of the Lower Miocene 

 period. 



Lignites and Clays of Bovey Tracey, Devonshire. — Surrounded by the 

 granite and other rocks of the Dartmoor hills in Devonshire, is a for- 

 mation of clay, sand, and lignite, long known to geologists as the 

 Bovey Coal formation, respecting the age of which, until the year 

 1861, opinions were very unsettled. This deposit is situated at Bovey 

 Tracey, a village distant eleven miles from Exeter in a south-west, and 

 about as far from Torquay in a north-west direction. The strata extend 

 over a plain nine miles long, and they consist of the materials of decom- 

 posed and worn-down granite and vegetable matter, and have evident- 

 ly filled up an ancient hollow or lake-like expansion of the valleys of 

 the Bovey and Teign. 



* Pengelly, preface to The Lignite Formation of Bovey Tracey, p. xvii. : Lon- 

 don, 1863. 



