MADREPORARIAN CORALS 



31 



possess only twelve tentacles and twelve mesenteries, but 

 in the great majority of the genera the number of tentacles 

 and mesenteries is very much greater than twelve when the 

 pol3^ps have reached their full size. 



The number of septa in a calyx does not always corre- 

 spond with the number of mesenteries in the polyp that 

 formed it ; but, generally speaking, when there are only 

 twelve mesenteries there are only twelve or six septa. In 

 the calices of polyps with a large number of mesenteries 

 there are usually a large number of septa. 



It has been suggested, therefore, that, in the first place, 

 the Madreporarian corals with polyps that have twelve 

 mesenteries should be placed in one sub-order, and those 

 with more than twelve mesenteries in another. There are 

 some difficulties, however, in accepting this division of the 

 group at present, as our knowledge of the anatomy of the 

 polyps of so many genera is imperfect, and a rearrangement 

 of our system of classification on imperfect knowledge would 

 be confusing and unsatisfactory. The best plan is to 

 accept the classification that is in general use as regards the 

 families, a classification which is based on the characters of 

 the corallum, and rearrange the order of these families on 

 the lines suggested by our knowledge of the anatomy of the 

 polyps. 1 



The arrangement suggested is as follows : 



Group A. — Polyps with more than twelve mesenteries. 



Family i. 

 Family 2. 

 Family 3. 

 Family 4. 

 Family 5. 



Turbinoliidae. 



Oculinidae. 



Astraeidae. 



Fungiidae. 



Eupsammiidae. 



^ For further information on the classification of the Madreporaria the 

 student should consult the beautifully illustrated memoirs by T. Wayland 

 Vaughan, entitled " Recent Madreporaria of the Hawaiian Islands and 

 Laysan," Smithsonian Instiattion Bull. 59, 1907, and " Shoal-water Corals 

 from Murray Island," etc., Carnegie Publications of Washington, 1918. In 

 these memoirs reference is given to other papers which are necessary for the 

 identification of specimens. P. Martin Duncan's A Revision of the Families 

 and Genera of the Madreporaria, published in 1884, is stiil-rcrf;:;ra9e4ltial 

 importance, and should be referred to. .^^*!^icV « VJ^ / 



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