2 A. H. Green — On Deep-sea Soundings. 



remains are preserved in tlie Chalk of Dover ? I am not surprised 

 that certain low forms should be common to the two, because the 

 conditions under which such creatures live do not in all likelihood 

 involve that struggle for existence to which specific change is 

 probably due ; they have ample space and ample sustenance for 

 animals of their simple requirements. Some few forms too, some- 

 what higher in the scale, seem to have lived on in "the dark un- 

 fathomed caves of ocean " but little affected by the round of changes 

 that have so largely altered the dwellers on the upper world, though 

 here it seems that the modern representatives are only generically 

 allied, and not specifically identical, with the older forms, a point of 

 the highest importance. But, leaving these cases out of the question, 

 are the two faunas, as a whole, a bit alike? Take one simple 

 instance. The older Chalk swarms with Ammonites, Scaphites, 

 Baculites and Belemnites, all well-marked and typical forms, not 

 one of which will be embedded in the Chalk of to-day ; and the old 

 Chalk has not yet furnished a single fragment of a marine mammal, 

 many species of which will be preserved in the modern Chalk. A 

 palaeontologist would readily point out any number of similar con- 

 trasts between the two faunas ; but what I have said will, I think, 

 make it clear why it is that I cannot understand how any one can say 

 we are living in the Cretaceous epoch, unless he at the same time 

 asserts that the age of a geological formation is to be determined 

 from those beds only which are formed out of Foraminifera, and by 

 the Foraminifera alone of the fossils contained in such beds. 



2nd. Dr. Carpenter very clearly explains the striking difference, 

 both in mineral character and fossil contents, between the deposits 

 now forming over the " cold area " overflowed by the frigid arctic 

 current, and the Globigerina-mud which is accumulating in the 

 " warm area " bathed by the more genial equatorial current ; and he 

 is uneasy lest the geologist of the future should, unless he is more 

 wide awake than the geologist of to-day, refer two such widely 

 differing deposits to epochs far apart, and, finding them occur side 

 by side, be led to the rash step of inserting a hypothetical fault 

 between them. 



I beg to assure Dr. Carpenter that no field-geologist would ever 

 run the risk of falling into such a blunder. The two areas, as Dr. 

 Carpenter states, interpenetrate one another ; their deposits will not, 

 therefore, be marked off from one another by a sharp boundary, but 

 will dovetail into each other over the sloping sea bottom, and there 

 will be a gradual blending of one into the other, both in lithological 

 character and fossil contents ; probably, too, the animals typical of 

 each area will, as they approach the uncongenial neighbourhood of 

 the other area, become step by step less numerous, and perhaps 

 dwarfed and stunted. These facts, noted in the field, will show 

 clearly to the geologist that he is not dealing with two deposits of 

 different ages ; in spite of the vast lithological and palaeontological 

 differences between the two groups of rocks, he will be able to trace 

 the gradual passage of one into the other, and he will thence con- 

 clude that they were accumulated at the same time, but under 



