2 SIDERASTREA RADIANS. 



from Vera Cruz and Colon on the mainland. It is equally plentiful on the 

 Florida Reefs and flats, and around the more northern Bermudas. Gregory 

 (1895, p. 277) records it as fossil from the Low-level Reefs of Barbados and 

 the Pleistocene Reefs of the Bahamas. 



A glance at the references shows that Siderastrea radians has been fre- 

 quently described and figured, but mainly as regards the corallum ; Le Sueur 

 (1820, p. 285), Pourtales (1871, p. 81), and Verrill (1901, p. 153) have, in addi- 

 tion, contributed brief notes upon the mode of occurrence of the living colonies 

 and the characteristics of the polyps. 



As Astrtza radians the species is thus systematically described by 

 Milne-Edwards & Haime in their " Histoire Naturelle des Coralliaires " 

 (vol. II, p. 506) : 



Polypary often fixed upon the Valuta turbincUus of Linnaeus, or spherical and free. 

 Budding takes place at the point of union of several calices. Calicos subpolygonal, appearing 

 thickened at the borders as a result of the strong development of the septal system, although 

 the walls are indicated only by fine lines. Columella formed by one or two compact tubercles, 

 scarcely visible, more distinct in young individuals. Three cycles of septa complete, and, in 

 general, a variable number of a fourth cycle, unequal. Interseptal chambers extremely 

 narrow. Septa much serrated, strong, very regularly crenulated at the border, nearly equal, 

 the primaries and secondaries a little larger. The teeth serrated, obtuse, and sub-equal. 

 The septa of the second cycle are fused by their internal border to those of the preceding 

 cycle. When the septa are broken from above they are found to be united by strong granules, 

 the spaces between the granules resembling small foramina. A specimen in this condition 

 has been considered by Lamarck as a distinct species under the name Astrcea picnctifcra. 

 In a vertical section the columella is compact and strong, the septa are perfect lamelte, cov- 

 ered with a radiating series of large granules ; the dissepiments are rudimentary, horizontal, 

 simple, and 0.5 mm. distant from one another. The species sometimes forms large masses. 

 The large diameter of the calices is from 3 to 4 mm., their depth z mm., or a little more. 



An excellent engraving of a colony is given in Ellis & Solander's 

 "Natural History of Zoophytes" (1786, plate 47, fig. 7), under the term 

 Madrepora galaxea. In his report on " The Stony Corals of Porto Rico," Mr. 

 Vaughan (1901) adds a photographic reproduction of a flat incrusting colony 

 and also one showing the enlarged calices (plates xv, xvi). In the plates 

 accompanying Prof. Louis Agassiz's " Report on the Florida Reefs " (1880) 

 are reproduced (plate xv) a dozen beautifully executed drawings represent- 

 ing the polyps and skeleton in some detail. Many of the actual details with 

 regard to the tentacles and septa are different from those observed on the 

 Jamaica 5'. radians, but there seems no doubt that the same species is 

 intended in each case. The drawings of the polyps are interesting as show- 

 ing for the first time the bilobed character of the tentacles and their irregular 

 arrangement at varying distances from the center of the disc. 



