TRANSACTIONS OF SECTION C. 765 
and the biologist must not look to the geologist for direct information concerning 
the dawn of life upon the earth. ; 
Proceeding now to a consideration of the faunas of the rocks formed after 
pre-Cambrian times, a rough test of the imperfection of the record may,be made by 
examining the gaps which occur in the vertical distribution of forms of life. If 
our knowledge of ancient faunas were very incomplete, we ought to meet with 
many cases of recurrence of forms after their apparent disappearance from inter- 
vening strata of considerable thickness, and many such cases have actually been 
described by that eminent paleontologist, M. Barrande, amongst the Paleozoic 
rocks of Bohemia, though even these are gradually being reduced in number owing 
to recent discoveries ; indeed, in the case of the marine faunas, marked cases of 
recurrence are comparatively rare, and the occurrence of each form is generally 
fairly unbroken from its first appearance to its final extinction, thus showing that 
the imperfection of the record is by no means so marked as might be supposed. 
Freshwater and terrestrial forms naturally furnish a large percentage of cases of 
recurrence, owing to the comparative rarity with which deposits containing such 
organisms are preserved amongst the strata. 
A brief consideration of the main reasons for the present imperfection of our 
knowledge of the faunas of rocks formed subsequently to pre-Cambrian times may 
be useful, and suggestive of lines along which future work may be carried out. 
That detailed work in tracts of country which are yet unexplored, or have been but 
imperfectly examined by the geologist, will add largely to our stock of information 
needs only to be mentioned ; the probable importance of work of this kind in the 
future may be inferred from a consideration of the great increase of our know- 
ledge of the Permo-Carboniferous faunas, as the result of recent labours in remote 
regions. It is specially desirable that the ancient faunas and floras of tropical re- 
gions should be more fully made known, as a study of these will probably throw 
considerable light upon the influence of climate upon the geographical distribution 
of organisms in past times. The old floras and faunas of Arctic regions are 
becoming fairly well known, thanks to the zeal with which the Arctic regions have 
been explored. But, confining our attention to the geology of our own country, 
much remains to be done even here, and local observers especially have opportuni- 
ties of adding largely to our stock of knowledge, a task they have performed so 
well in the past. To give examples of the value of such work, our knowledge of 
the fauna ot the Cambrian rocks of Britain is largely due to the present President 
of the Geological Society, when resident at St. David’s; whilst the magnificent 
fauna of the Wenlock limestone would have been far less perfectly known than 
it is, if it were not for the collections of men like the late Colonel Fletcher and 
the late Dr. Grindrod. Again, the existence of the rich fauna of the Cambridge 
Greensand would have been unsuspected, had not the bed known by that name 
been worked for the phosphatic nodules which it contains. 
It is very desirable that large collections of varieties of species should be made, 
for in this matter the record is very imperfect. There has been, and, I fear, is still, 
a tendency to reject specimens when their characters do not conform with those given 
in specific descriptions, and thus much valuable material is lost. Local observers 
should be specially careful to search for varieties, which may be very abundant in 
places where the conditions were favourable for their production, though rare or 
unknown elsewhere, Thus, I find the late Mr. W. Keeping remarking that ‘ it is 
noteworthy that at Upware, and indeed all other places known to me, the species 
of Brachiopoda [of the Neocomian beds] maintain much more distinctness and 
isolation from one another than at Brickhill.’!_ The latter place appears to be one 
where conditions were exceptionally favourable in Neocoméan times for the pro- 
duction of intermediate forms, 
A mere knowledge of varieties is, however, of no great use to the collector 
without a general acquaintance with the morphology of the organisms whose 
_Yemains he extracts from the earth’s strata, and one who has this can do signal 
___} W. Keeping, Sedgwick Essay: The Fossils and Paleontological Affinities of the 
Neocomian Deposits of Upware and Brickhill. Cambridge, 1883. 
