456 Transactions. — Geology. 



Shakespeare Cliff. At the latter spot the gi'avel bed lies immediately upon 

 the shelly stratum, but at Putiki a soft red sandstone, nou-fossiliferous, 

 intervenes. In fact, the district through which the Wanganui flows in the 

 lower part of its course contains a variety of local beds of limited area, and 

 beds of fossils completely different in character occur within a short distance 

 of each other, which, taken alone, might lead to the belief that the beds were 

 of different ages. Their synchronism is, however, indubitably proved by 

 their relative positions to the pumice, blue clay, and cemented gravel, which 

 are constant members of the series throughout the region, and, moreover, the 

 character of these fossils itself determines their age. It must be remembered 

 that molluscs, although possessing an organisation extremely simple compared 

 with that of many of the classes in the animal kingdom above them in rank, 

 and a great tenacity of life, are remarkably susceptible to surrounding 

 influences. An animal like the horse, with a highly complicated structure, can 

 range over many degrees of latitude and longitude and country of varied nature 

 without showing signs of being affected thereby, but to the humble Patella it 

 makes a vast difference whether its home be in a tranquil cave or on the 

 ocean beach, exposed to the constant buffe tings of the polyphloesbian sea. 

 Every bay, every harbour, every strand has its peculiar molluscan fauna, and 

 should, the embryos of a new species be accidentally conveyed into a new 

 habitat sufficiently hospitable to bring them to maturity, the form and 

 appearance of that species are speedily modified by an unseen and silent 

 working, but omnipotent, power into that fashion which best fits it for its new 

 residence. You can verify these statements for yourselves by diligently 

 examining and comparing the molluscs inhabiting Evans Bay with those of 

 Lyall Bay, or of the inner harbour of Port Nicholson. When, therefore, we 

 find the fossils of Shakespeare Cliff and of the Landguard Bluff differing 

 considerably in species, though not in genera, while in the one genera are 

 present which are absent from the other, we must not conclude their age to be 

 different on these grounds alone; but the lithological character of the strata 

 must be taken into account, and, above all, the type of the fauna. If that be 

 similar in both cases, we may conclude that the age of the strata is the same. 

 For while, from the Cambrian to the pleiocene eras, the multifarious forms of 

 molluscan life so blend with one another that it is impossible to say where one 

 ends and the other begins, still the naturalist who has made himself acquainted 

 with the entire fauna feels that certain periods are distinguished from each 

 other by the general typo of their fauna, although, in the present imperfect 

 state of human knowledge, he would bo unable to describe in words the nature 

 of that type. It is like the colours of the sky. Looking first at the zenith, 

 and then at the horizon, we perceive cleaily the difference of colour, but the 

 intervening tints pass imperceptibly into one another, and no imaginary zones 



