26 
THE GEOLOGIST. 
other— eight proofs, tlieii, that a passage did exist, unless we suppose 
that both areas ^vere tenanted from some more distant centre or 
centres of organic dispersion. It may be asked, were not these eight 
remnants of an older — a Silurian — {'auua, forms of life whose locali- 
zation had been determined by still earlier conditions ? Eight Silu- 
rian forms do make tlieir appearance amongst the fossils of Devon 
and Cornwall — are not these the very organisms ? Now it so happens 
that they are not. The Silurians spoken of are Favosites Jihrosa, 
Emmonsia hemisphcBrica, Ohonopliyllum perfoUatum, Atrypa aspera, 
A. reticulatus, Pterinea ventricosa, Clidophoriis ovatus, and Ortho- 
ceras imhricatum ; whilst the species coujmon to Lower North and 
South Devon are Favosites cervicorms, F. diibia, Fenestella arthritica, 
Stringocephalus Burtini, Spirifer aperturatus, Sp. Iwvicosta, Orthis 
f/ranulosa, and Clionetes sordida. In fiict, there is not one Silurian 
form recorded amongst the Lower North Devon series. This solu- 
tion, therefore, does not seem availnble. Shall we hold with Professor 
Phillips that "this unequal diffusion of definite forms of life may 
often be ascribed to oceanic currents" ?* I cannot but think that 
fewer difficulties attach to this than to any other hypothesis which 
has been proposed ; it simply requires us to suppose that a persistent 
oceanic stream, flowing through central Devon, separated the con- 
temporary deposits of the north and south, and, by its thermal or 
other qualities, formed an all but impenetrable barrier to the marine 
tribes. Moreover, whilst it would account for the limited organic 
distribution we are considering, it would not be out of keeping with 
the facts that a comparatively great number of species were common 
to continental Europe and Devon and Cornwall ; that of the fifty- 
eight species which passed over to the next succeeding Eauna, one 
only occurs in the carboniferous shales of North Devon, whilst all 
the others are found in central and northern England, Ireland, Bel- 
gium, Russia, and other distant localities ; and that a comparatively 
great number of forms are common to the upper areas of Cornwall 
and North Devon. 
Though, as we have seen, the test entirely fails, at least so far as 
Devonshire is concerned, on which scepticism respecting the existence 
of a Devonian period has been founded, namely, " that the blending 
of Silurian and Carboniferous corals is of common occurrence," yet if 
the word "fossil" is substituted for "coral," a blending of the kind 
certainly does occur, and doubtless the fact is not without a meaning. 
Eight species from the preceding period, and fifty-eight from tlie 
succeeding — a total of sixty-six — meet in Devon and Cornwall. 
Are they so many proofs that the rocks in wliich they were inhumed 
are not Devonian ? It must be borne in mind that there are two 
hundred and eighty-one species that are neither Silurian nor Carbo- 
niferous, but of an intermediate character. The palffiontological 
argument, then, stands thus: — There are sixty-six witnesses sup- 
posed to testify that the rocks are not Devonian, and two hundred 
and eighty-one — upwards of 4 to 1 — which emphatically declare that 
* Quart. Journ. Geol. Soc. vol. xvi. p. xl. 
