374 APPENDIX. 



Cenozoic time is divided into two ages, the Tertiary and the Qua- 

 ternary. The Quaternary age, the last in the geological series, com- 

 mences with the Glacial period, when, over Northern North America, 

 vast quantities of stones, gravel and sand, were transported by ice from 

 the north, and spread over the surface down to the parallel of about 40°, 

 and, of finer material still farther south along the great valleys, extend- 

 ing in the Mississippi Valley, as Prof. E. W. Hilgard has shown, even to 

 the Gulf of Mexico. The transportation was probably, for the most part, 

 the work of a continental glacier, covering a large part of the continent 

 north of 40°, and of the floods proceeding from its final melting. Europe 

 also had, at the same time, its northern glacier, reaching down to the 

 parallel of 50°, along which parallel the temperature is about the same 

 as on the parallel of 40° in North America. 



The Glacial period in North America was an era of greater continen- 

 tal elevation than now exists — at least for the glacial latitudes, that is, 

 from the parallel of 40° northward. It was followed by the Champlain 

 era, the era of a subsidence of the land below its present level, over the 

 same northern regions, which subsidence was accompanied by a modera- 

 ting of the climate, and a melting of the glacier. Next came the Terrace 

 era, marked by the elevation of the continent toward, and finally to, its 

 existing height, and a consequent making of terraces along river valleys, 

 around lakes, and on many sea borders. 



II. RADIATES. 



Polyps have been described as constituting one of the grand divisions 

 of Radiates. 



Radiates are characterized by a radiate system of structure, apparent 

 both externally and internally : in other words, they consist of different 

 series of similar parts repeated around a vertical axis. In polyps the 

 tentacles are thus repeated ; so, also, the internal septa ; the reproductive 

 system; the eyes, where these exist ; and so on through the structure. In 

 order to make this distinctive feature of Radiates more intelligible, a few 

 words are here presented on the other grand divisions of the Animal 

 Kingdom, or the Sub-Kingdoms as they are called. The number of 

 Sub-Kingdoms is five, as follows : 



1. Sub-kingdom of Vertebrates. — This designation refers to a fun-' 

 damental feature of the species, — the backbone or spinal column, con- 

 sisting of a series of bones (sometimes cartilaginous only), articulated to- 

 gether, called, in the Latin language, vertebrce. In connection with this, 

 they have a cavity above for the great nervous cord, and one below for 

 the viscera. Here belong Mammals (or Man, Quadrupeds, Whales, and 

 the like), Birds, Reptiles, Fishes. All other animals are invertebrates, 

 that is, have no vertebral column. 



