472 LICHENOPORID.E. 



or composed of many confluent disks, entirely adnate, or 

 partially free, and sometimes stipitate, developed on a thin 

 lamina, which usually forms a border round it. ZOCECIA 

 distinct or connate, in single radiating lines, or multiserial. 



D'ORBIGNY has constructed a large number of genera, 

 which are merely arbitrary groups based on very trivial 

 modifications of this well-marked type. Some of them 

 are included in the synonymy of the present genus ; and 

 others might have been added. 



The section in which the zoarium is made up of many 

 confluent disks offers perhaps the most marked varia- 

 tion ; but in such a species as L. hispida both the simple 

 and complex conditions of the zoarium are of about 

 equally common occurrence. The difference between the 

 species which have the cells in one series and those which 

 have them in two or more is of the very slightest moment; 

 and therefore I have not thought it necessary to relegate 

 L. regularis to the genus Actinopora, D'Orb. Still less 

 ground is there for separating the forms which are wholly 

 adnate from those which have the border free and raised 

 and the zoarium somewhat cup-shaped. 



The ooscium is represented in Lichenopora by an infla- 

 tion of the general surface of the disk, furnished with one 

 or more tubular and (usually) somewhat trumpet-shaped 

 orifices. 



The genus is widely distributed both in space and time ; 

 in the Cretaceous beds it is represented by a large number 

 of very beautiful forms. 



