INTRODUCTION. 3 



The species occurs plentifully in Kingston Harbor, Jamaica, from the 

 shore down to a depth of 5 or 6 feet. Here the colonies are small, and sub- 

 spheroidal or irregular in shape, partly or wholly incrusting some dead 

 shell or stone. Occasionally nearly globular colonies are obtained with the 

 polyps equally developed all over the surface. Such colonies lie exposed on 

 the sea-floor, or partly buried in beds of the aquatic phanerogam Tlialassia 

 marina^ and are associated with other free corals, such as Ma?iicina areolata 

 (Linn.), Cladocora arbuscula (Le Sueur), and Pontes divaricata (Le Sueur) ; 

 sometimes they are found incrusting shells inhabited by the living mollusc 

 or by hermit crabs. A flat incrusting form, growing upon stones and blocks 

 of coral, occurs on the coral flats outside the harbor in the area of reef 

 formation. Here the species may give rise to large fixed masses, 50 or 

 60 cm. across, while in shallow water the free colonies rarely exceed a 

 diameter of 10 cm. On the reefs S. radians is associated with another 

 common West Indian species of the same genus, viz, S. siderea (Ell. & Sol.). 

 This latter may produce large heraispheroidal blocks, and in situ is readily 

 distinguished from 5. radians by the larger size of the polyps and their 

 reddish brown color. 



S. radians seems peculiarly hardy as regards the conditions under which 

 it will thrive. The shore waters within Kingston Harbor are often muddy 

 from the action of the strong day breezes, and at times the living polyps are 

 covered by deposits of sand and mud. Around Jamaica, however, the colo- 

 nies are rarely exposed to the direct rays of the sun, the fall of the tides 

 being very restricted ; but further north, where the diflPerence between high 

 and low tides is greater, both Pourtales and Verrill have found specimens 

 so situated that they are frequently subjected to the direct rays of the sun. 

 With regard to the occurrence of 5. radians in Florida, Pourtales, in " Deep- 

 Sea Corals" (1871, p. 81), writes: 



In altitude it ranges higher than any other coral of the Floridian fauna, as small masses are 

 found flourishing in pools left by the tide. I have even seen small clusters left partially dry in 

 a hot sun, keeping up a communication with the water only by a few of the lowest polyps of 

 the group. From their position they must frequently have been thus exposed without incon- 

 venience. According to Prof. Agassiz the polyp has bilobed short tentacles at different 

 distances from the center. 



Prof. A. E. Verrill (1901, p. 154) gives the following notes as to the 

 conditions under which the species is found at the Bermudas : 



This species, which is abundant at the Bermudas, is more hardy than most reef corals, 

 for it can live and grow well in shallow water on mud flats, where it is laid bare by nearly 

 every tide, and where most other corals would be smothered in the mud, though 5". siderea 



