William Pengelly

“ It appears, then, that the genera found in the Devonian era, as represented in Devon and Cornwall, even when those peculiar to it are included, yield a less aggregate number of species, that the average number of species per genus is smaller, and that the genera having their maximum specific development are fewer in Devonian than in either Silurian or Carboniferous times, and that in each of these particulars the Carboniferous surpasses the Silurian age. ”

“ Suppose it true that in some cases the organic dissimilarity which has been described was due to a difference in the mineral character of the ancient sea-bottom, such as was mentioned in the case of Lower South Devon and Lower Cornwall; still, when we have two areas, like Lower South and Lower North Devon, consisting of con- temporary, almost contiguous, and scarcely dissimilar deposits, one rich and the other poor in the variety of its organic remains, having together two hundred and four species with no more than eight in common, some other solution is obviously required. ”

“ We are prepared, by even a slight acquaintance with the geographical distribution of existing organisms, to find that deposits strictly contemporary, lithologically similar, and closely connected geographically, have certain fossils peculiar to each; but, unless we recognize time as a factor, it will be difficult to explain the following striking results in Petherwin and Barnstaple. Together they have yielded as many as one hundred and thirty-one species of fossils, yet have no more than seventeen in common ”

“ Every genus of the classes Amorphozoa, Zoophyta, and Brachiopoda occurs in South Devon, and with the exception of Cephalopoda it contains a greater number of genera in each class than either of the other areas. All the genera of Cephalopoda appear at South Petherwin. ”

“ The last, or "Future," consists of two series, namely, 1st, those genera which are equally represented in the two sets of beds; and 2ndly, those that are not; evidently the last series alone can supply information on the question under consideration. It is made up of the fifteen genera named in the following table, in which the columns headed P., B., C, exhibit the number of species, belonging to each genus, which occur in the Petherwin, Barnstaple, and British Carboniferous beds respectively. ”

“ Forty- one of these fifty-six genera contain each but a single species in the British Devonian deposits. The only genera thus limited that can be said to be rich in species are Stromatopora, Acervularia, and Clymenia. The first, a genus of Amorphozoons, contains five species, all limited to South Devon; the second, a group of corals belonging to the great Palæozoic family Cyathophyllidæ, contains five species, all peculiar to South Devon ”

“ Are the notions of biologists respecting specific distinctions, whatever they may be, sufficiently mature and uniform to warrant our relying on them? Something must doubtless be conceded on each of these points, but still there cannot but be a large outstanding quantity of fact incapable of being thus explained away. ”

“ Are we to believe that our knowledge of the geological record is too imperfect to warrant any important generalizations? Do our museums fully represent the fossilized remains of bygone forms of life? Are all the extinct organisms which have been exhumed registered in the published lists? ”

“ It is only accessible from the sea, and is situated at the apex of a small cove, the mouth of which is a passage, probably about twenty feet wide, between two walls of limestone; within it is somewhat wider. Except at high-water, a small, steep, terraced, shingle beach lies between the sea and the mouth of the cavern. The cove is simply a gallery, at least eighty feet long, about four feet wide, in some places not more than three feet high, but commonly high enough for a man to stand erect. ”

“ Doubtless the fact that the Carboniferous forms so greatly outnumber the Silurian has a meaning. Does not this greater organic affinity betoken a closer connection with the more modern than with the more ancient period? ”

“ The very limited distribution in space of the last of the trio would scarcely suggest the thought that such an organism would be likely to be capable of enduring thermal and other physical changes such as, there are reasons for believing, considerable lapses of time introduce into any given area, changes probably not dissimilar to those experienced in passing to a distant locality in any one and the same period. ”

“ It must be understood that any one of the ten columns just noticed shows, not the total number of species common to the areas the initials of which stand at its head, but simply the number at once common and restricted to them collectively ”

“ The sea had also carried in some evidences of the existence of man; amongst other things I remember a portion of a tin kettle and a fragment of a basket, of the coarse kind used on board colliers and other ships. ”

“ The first of these groups—which alone we have to consider here—contains thirty-one genera, of which six may be said to belong to the Past, and twenty-five to the Future, the age of Petherwin and Barnstaple being the chronological stand-point.
The first, or "Past" division, does not contain a number sufficiently great to be of service in this inquiry. ”