3. The next series, or middle fresh-water and estuary marls, are distinguished
by the presence of Melania fasciata, Paludina lenta, and clays with Cypris; the
lowest bed contains Cyrena semistriata (Figure 159), mingled with Cerithia and a
panopaea.
4. The lower fresh-water and estuary marls contain Melania costata, Sowerby,
Melanopsis, etc. The bottom bed is carbonaceous, and called the "Black band," in
which Rissoa Chastelii (Figure 162), before alluded to, is common. This bed
contains a mixture of Hempstead shells with those of the underlying Upper Eocene
or Bembridge series. The mammalia, among which is Hyopotamus bovinus, differ, so
far as they are known, from those of the Bembridge beds. Among the plants,
Professor Heer has recognised four species common to the lignite of Bovey
Tracey, a Lower Miocene formation presently to be described: namely, Sequoia
Couttsiae, Heer; Andromeda reticulata, Ettings.; Nelumbium (Nymphoea) doris,
Heer; and Carpolithes Websteri, Brong. (Pengelly, preface to The Lignite
Formation of Bovey Tracey page 17. London 1863.) The seed-vessels of Chara
medicaginula, Brong, and Chara helicteres are characteristic of the Hempstead
beds generally.
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