452 
ELEMENTS OF GEOLOGY. 
the Devonshire fossils. The Cyathophyllum ccespitosum (Fig. 
514) and Ileliolites pyriformis (Fig. 512) are species peculiar 
to this formation. 
With the above are found no les§ than eleven genera of 
stone-lilies or crinoids, some of them, such as Cupressocrini- 
tes^ distinct from any Carboniferous forms. The mollusks, 
also, are no less characteristic; of 68 species of Brachiopoda, 
ten only are common to the Carboniferous Limestone. The 
Stringocephaliis JBurtini (Fig. 515) and Uncites Gryphus 
Fig. 515. 
Fig. 516. 
Stringocephalus Burtini, Def. 
a. Valves united, b. Interior of ventral or large 
valve, showing thick partition and portion of 
a large process which projects from the dorsal 
valve across the shell. 
Uncites Gryphus,’IDef. 
Middle Devonian. 
S. Devon and the 
Continent. 
(Fig. 516) may be mentioned as exclusively Middle Devo¬ 
nian genera, and extremely characteristic of the same divis¬ 
ion in Belgium. The Stringocephalus is also so abundant 
in the Middle Devonian of the banks of the Rhine as to have 
suggested the name of Stringocephalus Limestone. The only 
Pio. 51 ^ two species of Brach¬ 
iopoda common to 
the Silurian and De¬ 
vonian formations are 
Atr yp a reticularis 
(Fig. 532, p. 462), 
which seems to have 
been a cosmopolite 
species, and Strophe- 
mena rhomboidalis. 
Among the pecul¬ 
iar lamellfbranchiate 
bivalves common to 
the Plymouth lime¬ 
stone of Devonshire 
and the Continent, 
we find the Megalodon (Fig. 517). There are also twelve 
genera of Gasteropods which have yielded 36 species, four of 
which pass to the Carboniferous group, namely Macrocheilus^ 
Megalodon cucullatus, Sow. Eifel; aiao Bradley, 
S. Devon. 
a. The valves united. . b. Interior of valve, showing 
the large cardinal tooth. 
