382 BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



The columella is large, trabecular, with a papillate upper surface; 

 diameter, as much as 4 mm. The columellar elements are rather 

 often twisted and present a whorled appearance. 



Endothecal dissepiments rather delicate; exotheca, coarse and 

 very vesicular. 



The calices of the other kind (pi. 87, fig. la) in their typical devel- 

 opment are smaller than those above described, their edges are 

 only slightly elevated, and the septa and costae are decidedly thin 

 and exsert. Diameter of the calices from 5 to 8 mm. ; septal margins 

 2 mm. tall. 



The differences between these two kinds of calices are so great 

 that it seems scarcely possible that they could belong to the same 

 species; however, they occur on the same corallum where perfect 

 intergradation can be traced. 



Pourtales, as far back as 1871, 1 published the following important 

 notes on this species: 



There is considerable variation among the specimens from Florida in the Museum of 

 Comparative Zoology, enough apparently to warrant placing them among the three 

 species mentioned in the synonymy; but by carefully examining the different parts 

 of each specimen, passages from one to the other can be found. Thus young polypi- 

 doms, expanding rapidly laterally and with rather distant polyps, appear at first to 

 differ considerably from strongly convex ones with crowded calices; the costae are 

 larger, flatter, and less sharply denticulate, and the border of the calicles less elevated. 



The size of the calicles, relied on to divide the genus into groups by Milne Edwards 

 and Haime, is a very uncertain character; one specimen has in one part the calicles 

 varying from 3.5 to 4 mm., in another from 7 to 8 mm. The same specimen has in 

 some parts the contiguous walls united solidly, with very few or no exothecal cells, in 

 others separated by an abundant cellular exotheca. In worn specimens the last cycle 

 disappears first, for that reason probably Orbicella (Madrepora) radiata Ellis has been 

 characterized by the Milne Edwards and Haime as having but three cycles. 



Verrill gives the following description : 2 



Much of the confusion in regard to the name of this species is due to the fact that it 

 was generally described and figured from badly beach-worn specimens by the earlier 

 writers. Such specimens have the septa and calicles worn away and the hard ex- 

 otheca thus becomes prominent around the excavate calicles, so as to greatly change 

 the appearance of the coral. Another cause is the rather wide variations in the size 

 of the calicles. 



The normal or average specimens have the calicles about 6 to 8 mm. in diameter, 

 but occasionally a specimen occurs in which part or all of them may be 9-10 mm., or 

 rarely, even 11 mm. in diameter. Sometimes, on crowded parts of large specimens, 

 the diameter may be only 4 to 5 mm. The degree of elevation of the calicles is also 

 more or less variable on a single specimen. 



The calicles may be pretty close together, where crowded, but in other cases they 

 are separated by spaces of 4 to 6 mm. or more. The costae are usually well developed 

 as denticulated, rounded, radial ribs, usually 48 in number. 



The septa are generally about 48, arranged in four regular cycles, but several of 

 those of the last cycle are often rudimentary or lacking, reducing the number to 40-44. 



i Mus. Comp. Zool. 111. Cat., No. 4, p. 76. 



2 Trans. Conn. Acad. Arts and Sci., vol. 11, pp. 102, 103, 1902. 



