ON A PIECE OF CHALK 73 



ammonites and belemnites which are so characteristic of the 

 period preceding the cretaceous, in like manner die with it. 



But, amongst these fading remainders of a previous state 

 of things, are some very modern forms of life, looking like 

 Yankee pedlars among a tribe of Red Indians. Crocodiles of 5 

 modern type appear ; bony fishes, many of them very similar to 

 existing species, almost supplant the forms of fish which pre- 

 dominate in more ancient seas; and many kinds of living 

 shell-fish, first become known to us in the chalk. The vegeta- 

 tion acquires a modern aspect. A few living animals are not 10 

 even distinguishable as species, from those which existed 

 at that remote epoch. The Globigerina of the present day, 

 for example, is not different specifically from that of the chalk ; 

 and the same may be said of many other Foraminifera. I 

 think it probable that critical and unprejudiced examination 15 

 will show that more than one species of much higher animals 

 have had a similar longevity ; but the only example which I 

 can at present give confidently is the snake's-head lamp-shell 

 (Terebratulina caput serpentis), which lives in our English seas 

 and abounded (as Terebratulina striata of authors) in the 20 

 chalk. 



The longest line of human ancestry must hide its diminished 

 head before the pedigree of this insignificant shell-fish. 

 We Englishmen are proud to have an ancestor who was present 

 at the Battle of Hastings. The ancestors of Terebratulina 25 

 caput serpentis may have been present at a battle of Ichthy- 

 osauria in that part of the sea which, when the chalk was form- 

 ing, flowed over the site of Hastings. While all around has 

 changed, this Terebratulina has peacefully propagated its 

 species from generation to generation, and stands to this day, 30 

 as a living testimony to the continuity of the present with the 

 past history of the globe. 



Up to this moment I have stated, so far as I know, nothing 



