THE RECORD FROM FOSSILS. IOI 



the Paleozoic (2-4) age, and it was not until the later part or the 

 Mesozoic (5-8) that the modern forms began to appear, and the class 

 assumed its present condition. How far this late origin of most of our 

 existing groups is due to the lack of preservation of animals which 

 really existed in the early ages, cannot be positively determined. The 

 great probability is that most of our modern orders are much older 

 than their fossils would lead us to believe. 



Aciinozoa (this includes the corals and the sea anemones). The 

 corals have commonly a lime skeleton, and are quite well adapted for 

 preservation. They have been very abundant in all ages. The 

 Silurian (2) rocks contain five of our modern orders, though most of 

 the corals were quite unlike their modern representatives. The orders 

 most abundantly represented at that time are, however, not the 

 orders most abundant to-day. During all the Paleozoic (2-4) they 

 continued to live in abundance, a large variety of forms being in 

 existence all through that time. With the Mesozoic (5-8) however, 

 we find the modern forms of corals becoming more abundant, and 

 from that time the production of the modern coral was a matter 

 of slow and constant growth. 



The Ctenophora are wholly unrepresented as fossils, owing to their 

 soft jelly-like composition. 



In general, then, the Coelentera form an ancient group, appear- 

 ing in abundance in the earliest rocks, and being numerous in all 

 ages. During the Paleozoic, however, the types represented were 

 not those most abundant to-day, and many of them were confined to 

 the Paleozoic (2-4). The modern Coelentera seemed, so far as our 

 record goes to-day, to have appeared with the Mesozoic (5-8), some 

 of the ancient types disappearing entirely at that time and others 

 becoming of subordinate importance. At this time also there was a 

 great multiplication of sub-orders and families. 



ECHINODERMATA. 



This sub-kingdom is divided into five classes : Crinoidea, Aster- 

 oidea (star-fishes), Ophuroidea (brittle stars), Echinoidea (sea urchins), 

 and Holothuroidea. 



Crinoidea (stalked echinoderms). This class may be especially 

 regarded as the fossil class of the group, for although some are still 

 in existence to-day, they are very few in numbers (only eight genera), 

 and mostly confined to deep seas. In early geological times they 



