Geological Distribution of the Rhabdophora. 449 the mouth-organs and eyes, showed the same structure, in equal detiniteness and perfection, as the larger castes. Allu-sion was also made to the ravages of these destructive insects ; and some of the modes for exterminating them were ex-plained. XLIX. — On the Geological Distribution of the Rhabdophora. By Charles Lapworth, F.G.S. Part I. Historical. [Continued from p. 257. J (d) Recent Research. Geological. — It has been already shown that those geologists whose leanings were mainly palaiontological accepted without question the reference of all prolific Graptolite-bearing strata to the general horizon of the Llandeilo formation, and endeavoured to escape from the numerous difficulties in which they conse-quently found themselves involved by appeals to the recog-nized rule of the restriction of certain fossil groups to special sediments, by references to the phenomenon of migration, by the adoption of the theory of " Colonies," and the like. But there were, in addition, a few influential geologists who looked upon geology almost wholly from the physical side, and who naturally relied only upon such palaeontological testi-mony as distinctly coincided with the inferences they drew from the stratigraphical evidences. These viewed all attempts to correlate strata of disconnected areas by means of the Rhabdophora with the gravest suspicion, passing over with a careless indifference the clearest indications of a natural suc-cession afforded by those entered upon their fossil lists. When, as occasionally happened, the paleeontological testimony af-forded by these fossils conflicted with that drawn from the apparent physical evidences, no matter how scanty or ambi-guous, they at once set it aside with undisguised contempt. However mortifying it may be to the graptolithologist to admit the fact, it cannot be denied that this course was at all events quite as reasonable as the habit of the over-credulous majority. The cautious field-geologist, on consulting the Avorks of those who had made these fossils the subjects of special study, learnt at once that, according to the best autho-rities, many of the most characteristic Llandeilo Graptolites of Britain occurred in America in the very highest beds of the
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