Chap. XL] 
LOWER DEVONIAN FOSSILS. 
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tinent. Large species of Homalonotus (H. Herschelii) &c, different from the 
Ludlow species, being ornamented with spines, characterize the lowest beds. 
They are found, too, in Devonian strata of very distant regions, e. g. the Cape of 
Good Hope. Trilobites, however, which swarmed in Silurian times, were com- 
paratively scarce in the Devonian: although several of the very numerous genera 
of the former era are known in it, no new genera are introduced. 
Among the Mollusca, nearly all the species of Atrypa, Orthis, and Spirifer 
differ from those of the Silurian era *. One shell, however, Atrypa reticularis, 
must be mentioned as an exception to the prevalent rule of each great group 
being distinguished by peculiar forms j for this hardy species, with which the 
reader became familiar in the Silurian rocks (see p. 210), lived on to the Devo- 
nian era, and is as common in the limestones and shale of Devonshire as in the 
older series. It even ranges to the furthest known geographical limits of the 
Devonian rocks — to Armenia, the Caucasus, and China on the east, and to 
the Devonian deposits of America on the west ! 
Although many of the Silurian and Devonian genera are the same, yet the 
proportional number of species is very different, and certain genera of Shells 
which were common in the older period are no longer traceable. Thus the 
genus Orthis becomes far less abundant, whilst Spirifer, comparatively rare in 
the older rocks, augments much in variety of forms, and especially in the size of 
the shell — the large broad- winged Spirifers being especially characteristic of 
rocks of this age, and particularly in the Lower Devonian of several foreign 
countries. Several species of Brachiopods common in the sandstones of Torquay 
andFoweyin South Devon and Cornwall are, indeed, well known in the Rhenish 
Provinces. Such, for example, are Spirifer micropter, Goldf. (Sp. hystericus, 
Schl.), Sp. laevicosta, Valenc. (Sp. ostiolatus, Scbl), Chonetes sarcinulata, 
Hupsch (Ch. Hardrensis, Phill.). In Britain, no Brachiopod is more typical 
than Atrypa desquamata, Sow., Foss. 74. f. 5. 
Tentaculites ahnulatus, Schl., a species of Homalonotus (probably armatus, 
Burm.) with spines, and the remarkable Rhenish Coral Pleurodictyum proble- 
maticum, Goldf., are among the characteristic species of the lowest beds. 
As if to draw the parallel even still closer between Devonshire and the 
Rhine, Bactrites (Orthoceras) gracilis, Minister, the prevailing fossil of the 
Wissenbach slates (which, as will hereafter be seen, occupy a low position in 
the series) has been found at Black Head near St. Austel. 
The most typical Shells which mark the strata in which they occur as of 
Middle Devonian age are the large Stringocephalus Burtini, Defrance, Foss. 74. 
f. 4, Megalodon cucullatus, Sow., f. 2, together with Murchisonia bilineata, 
Phillips, f. 3 (M. bigranulosa, d'Archiac), and the Corals Cyathophyllum 
csespitosum, Goldf., Heliolites porosus, Goldf., and Calceola sandalina, Linn., 
Foss. 74. f. 1. 
To these few characteristic fossils the following may be added as abounding 
in the limestones of Plymouth, Berry Head, Teignmouth, Ogwell, and part, at 
least, of those of Newton Bushel t, viz. : — Spirifer speciosus, Schloth., Cyrtina he- 
teroclyta, Defrance, Pentamerus brevirostris, Phill., Cyrtoceras ornatum, Goldf., 
&c. ; species of Scoliostoma (or Vermetus ?), Euomphalus annulatus, Phill., 
Pleurotomaria, Macrocheilus, Loxonema, Acroculia, and Porcellia; Encrinites 
* Many Silurian species appear, indeed, in eata- Khynchonella cuboides, Sow., a species which 
logues of Devonian fossils, but in most cases, it characterizes the beds immediately below the 
is believed, (with the exception of a few Corals) Clymenia-limestones of Germany and Belgium, 
erroneously. A species of Chiton (the elongate form, Helmin- 
t The higher beds at Newton Bushel are cer- thochiton) is also found in the Newton Bushel 
tainly of newer date, the characteristic Shell being beds. 
