102 



PROF. J. LOGAN LOBLEY, F.G.S., F.R.G.S._, ON 



The graptolites are also confined to Palaeozoic rocks, but they 

 were structurally similar to the Sertularians or sea-pens of the 

 present day. Their habitat was similar, the functions of their 

 organs were similar, their life was similar. 



And so it may be said of the still older Oldhamia of the lower- 

 most Cambrians that has not been found in any less ancient 

 rocks, for it was structurally similar to some Hydrazoa of to-day. 

 In Cambrian rocks, too, are fossil lamellibranchs and gasteropods 

 of families that flourish in our own seas, as the Arcidse, the 

 NuculidcT, and the Patellidae, while Silurian genera of these 

 Classes allied to living genera are numerous. These were in all 

 respects similar to living species in all essentials of structure 

 and physiological function. Again, the small Class Pteropoda 

 that gives the little Clio horecdis as food to the great Whale of 

 northern seas, gave the Coimlaria to Silurian seas, and specimens 

 of these have been so wonderfully preserved that their fine 

 striations, exactly like the fine striations of the glassy shells of 

 the living Clin, are most distinctly seen. 



In Cephalopoda, with one exception, Palaeozoic generic forms 

 were markedly different, it is true, from later and recent forms. 

 The straight, the swollen, and the slightly curved forms of 

 Tetrabranchiata, so abundant in Pal'cieozoic rocks, are almost 

 absent from Secondary* and quite absent from Tertiary forma- 

 tions, and the shell-less Dibranchiata that gave the multitudes 

 of belemnites to the Jurassic and Cretaceous rocks, were absent 

 from Pala'ozoic seas. Yet the essentials of the cephalopod of 

 to-day were present in the Palaeozoic cephalopods, and the 

 chambers, and septae, and the siphuncle of the living Nautilus, 

 were matched by the chambers and septae, and the siphuncle of 

 the Lower Silurian Orthoceras, which was also four-gilled and 

 so in the same Order, Tetrabranchiata. The exception is the 

 Nautilus itself, that not only has remained true to its Class, its 

 Order, and its Family, but al^^o to its genus from Palaeozoic times 

 to the present. Through all the varying marine conditions, the 

 varying character of deposits, and the varying temperatures 

 during the long t^eons between the Palaeozoic epoch and to-day, 

 the Nautilus has lived, and it is now flourishing in great abun- 

 dance in the Indian and Pacific Oceans as Nautilus po^njnlius, 

 the well-known " pearly nautilus." 



The corals have lost an Order, but all the Palaeozoic coral 

 animals had the same physiological powers based on the same 

 organs, with the same functions, as the corals of our present 



* Tlie jfenus Orthoceras occurs in the Al])i)ie Trias. 



