21 



extremity when you build up the ordinary Scaphite ; or you can take 

 care the parts do not touch when there is immediately presented 

 to you Ancyloceras (fig. 16); or you can increase the radius, cut 

 off the end, and you behold Crioceras (fig. 17). 



These variations upon the general arrangement of the twists are 

 essentially Cretaceous, for though one or two are known to have 

 existed before the Cretaceous beds were deposited, it is in the sands 

 and clays of this formation that they were at a maximum, some on 

 one horizon, some on another, and then they died. 



A few more words and I will cease to weary you. The Nautilus 

 (see Fig. 3), living in the present seas, dates back its ancestors into 

 remote ages, a very noble member of the aristocracy of shells. 



Far removed in the Silurian times, with forms of life which have 

 long since passed away, the Nautilus sprang into existence. It knew 

 of the foliage of the Coal-bearing districts ; of the Coral-reefs which 

 arose in Oolitic days ; of the vast stream which furnished the broad 

 expanse of the Wealden Delta ; of Mammals coming into being, and 

 of the Fish 1 putting off their bony armour ; of the bright Spice Islands 

 that flourished where we now have our ships of war ; of the change 

 in climate in the northern lands from tropical heats to polar 

 frosts ; — it saw man a mere savage, working with flint tools ; then 

 better instructed, forming an iron ploughshare ; lastly, busy with 

 his merchandise, master of the electric current, putting his girdle 

 round the world, and speaking with the tongue of the lightning's 

 flame. 



Like the Ammonite, the Nautilus had relatives of similar organiza- 

 tion, but clothed in diverse frames ; now being straight, as in the case 

 of the Orthoceras ; now copying a bishop's crook, as the Lituite ; 

 now a rough double cone, as the Gomphoceras ; now of a curved 

 pear form, as the Phragmoceras ; now with the whorls not in one 

 plane, as the Trococeras ; now evolute, as the Cyrtoceras. All these 

 creatures of the Nautilus tribe were of the ancient times, fitted no 

 doubt for a special office, suited for requirements and conditions 

 lasting whilst they swam in the old waters in the pursuit of prey as 



1 The modern representatives of the armour-plated fish, such as the Sturgeon, etc., 

 are now in the minority. 



