1869.] 



on the Scientific Exploration of the Deep Sea. 



451 



(§61), several Arenaceous forms (some of them new) were extremely abun- 

 dant ; but in addition to these we found a great abundance of Miliolines 

 of various types, many of them attaining a very unusual and some even an 

 unprecedented size. As last year, we found Coniuspirce resembling in 

 general aspect the large Operculince of tropical seas, and Bilocuhnce and 

 Trihculince far exceeding in dimensions the littoral forms of British shores ; 

 and with these were associated Cristellarice of no less remarkable size, 

 presenting every gradation from an almost rectilineal to the Nautiloid form, 

 and having the animal body in so perfect a state as to enable it to be com- 

 pletely isolated by the solution of the shell in diiute acid. — It is very in- 

 teresting to remark that certain forms of this Cristellarian type are among 

 the most characteristic Foraminifera of the Cretaceous as well as of various 

 Tertiary deposits ; and the similarity of some of these to existing forms 

 is so close, that the continuity of the type from the Cretaceous epoch cannot 

 be reasonably questioned. It is further interesting to note that it has a 

 great bathymetrical range, no difference showing itself between the Cris- 

 tellarians of our Warm area and those found in the preceding Cruises 

 at nearly three times the depth. — The continuity of Foraminiferal life is 

 further indicated by the occurrence in the Globigerina-ooze of a number 

 of Rotalian forms which are peculiarly characteristic of the Fauna of 

 the Cretaceous period. 



88. The cumulative evidence which we have thus obtained in support of 

 the hypothesis advanced last year ('Lightning' Report, p. 193) as to the 

 uninterrupted continuity of the Cretaceous deposit on the North- Atlantic 

 Sea-bed from the epoch of the Chalk-formation to the present time, will be 

 more fully discussed hereafter. But as, with the exception of the subse- 

 quent dredging in the shallow waters of the Minch already referred to 

 (§ 86), our Zoological exploration of the sea-bottom came to a conclusion 

 with the extraordinary climax just described, we may here mention an idea 

 which formed the subject of much discourse between us at this period. 



89. It is, we believe, the general creed of modern Geologists, that all 

 Calcareous rocks have had, either directly or indirectly, an Organic origin ; 

 and that the most perfectly mineralized condition of such rucks affords no 

 evidence to the contrary, there being abundant evidence that all traces of 

 organic structure may be completely obliterated by subsequent metamor- 

 phic action. Thus upheaved masses of recent Coral are frequently converted 

 into subcrystalline Limestone, the organic origin of which would not be 

 recognized by any feature in its molecular arrangement or composition ; 

 whilst a change often presents itself (as on the Antrim Coast) of a true 

 Chalk into a subcrystalline Marble, under the combined influence of the 

 heat and pressure occasioned by the intrusion of Volcanic rocks. Now 

 since there can be no question that the Chalk-formation in its entirety owes 

 its origin chiefly to the accumulation on the deep-sea bottom of the shells, 

 or their de'bris, of successive generations of Foraminifera which lived and 

 moved and had their being there, — and since there can be as little question 



