dM THE NEW EVOLUTION 



of which died out in the relatively recent past, leaving 

 the present seas with only the chambered nautilus and 

 its few close relatives. 



Together with the nautiloids in the very ancient 

 seas there flourished the ammonites (figs. 33, 34, 

 p. 55), creatures which were very similar but vastly 

 more numerous and varied. Of these more than 5 ,000 

 different kinds have been described. All of the am- 

 monites are now extinct— in fact none of them sur- 

 vived beyond the end of the age of reptiles (the 

 Cretaceous period). 



A curious thing about the ammonites is that they 

 first appeared after the nautiloids had begun to wane. 

 After the end of the so-called palaeozoic era they 

 increased with great rapidity both in numbers and 

 in variety. At the end of the Cretaceous they sud- 

 denly disappeared, just as did the giant reptiles, for 

 what reason we do not know. Some of the ammo- 

 nites were very small, appearing as mere specks, but 

 some were very large forming a close spiral four feet 

 or more across. 



In few groups of animals is the fossil record so com- 

 plete and satisfactory as it is in the ammonites, and 

 in few groups are progressive developmental lines so 

 clearly indicated. 



The history of the brachiopods or lamp-shells (fig. 

 60, p. Ill) is an interesting one. More than 7,000 

 different kinds are known of which only about 160 

 are to be found living in the present seas. Brachio- 

 pods are well represented in the very earliest rocks 

 which contain recognizable fossils — the rocks of the 



