xvm 



FACTS AND OBSERVATIONS. 



ECHINODERMATA. The following little Table represents, numerically, the geographical distribu- 

 tion of the three forms of the class Echinodermata. It is short, but contains much matter. 



TABLE K. Class Echinodermata (Geographical Summary) . 



Table L, subjoined, shows the numerical proportions in which the species of this class occupy 

 the successive stages of this epoch. 



TABLE L. 



Its contents require no remarks. 



Crinoidea. The order Crinoidea contains 78 genera and 315 * species. Thirty genera have 

 each only one species ; and these in only five cases occupy two countries. Fifteen genera have three 

 species, and ten have two, the geographical range being here also short. A few genera are com- 

 paratively rich in species. Thus Glyptocrinus has nineteen species, and is found in fourteen 

 distinct areas ; and Actinocrinus has fourteen species, and inhabits fourteen areas ; Hypantho- 

 crinus, with twenty- three species, is seen in ten districts. Together with great beauty, Crinoids are 

 very sensitive to conditions, and therefore they have but a limited geographical range. 



The Table K will show how few Crinoids there are in many countries, such as Nova Scotia, 

 Newfoundland, Iowa, Scotland, Spain, India, Tasmania, &c. Crinoidea have in North America 

 two principal foci or places of concentration. There are likewise in Europe two similar chief seats. 

 They are all singularly rich. 



These concentrations are in America some hundreds of miles apart : that on the west occupies 

 Tennessee, Illinois, Wisconsin ; and that on the east is met with around the City of Ottawa (Canada 

 West) and North New York, the adjacent state of the North- American Federation. 



The chief seats in Europe of this order are England with Wales, and Russia with Sweden, and 

 this in a very striking manner. These remarkable assemblages are probably due to appropriate 

 sediments and other favourable conditions (deep sea &c.) . 



A genus may be confined to a very few square miles, as in the case of the subgenus Cupellcscrinus 



* 315, from late acquisitions. 



