FORAMINIFERAN AND OTHER CORALS 183 



Fig. 90. — Sporadatrema cy- 

 Undricum from Providence 

 Island, Indian Ocean, 70 

 fathoms. :'. 2 diams. 



genus is not known to occur in the Mediterranean Sea or in 

 the West Indies. 



In the case of Polytrema and Homotrema the specimens 

 from various parts of the world are 

 so much ahke, both in form and 

 minute structure, that it is reason- 

 able to suppose there is only one 

 species of each genus ; but in the 

 case of Sporadotrema it is necessary 

 to divide the genus into two species, 

 5. cylindricum and 5. mesentericum. 

 The form of Sporadotrema cylin- 

 dricum is always erect, a thick solid 

 stem springing from a restricted base 

 and giving rise to a few thick 

 branches (Fig. 90). No flat disc- 

 shaped encrusting specimens have 



yet been found. The surface of the stem and the proximal 

 parts of the branches are perforated by a number of 



foramina of relatively large 

 but variable size and irregu- 

 larly scattered. There are no 

 areolae and no pores (Fig. 88, 

 C). In some specimens, the 

 chambers of whicli the corals 

 are composed (Fig. 91) are 

 indicated on the surface at the 

 ends of the branches by a 

 number of convex areas per- 

 forated by relatively large 

 foramina. 



Another very striking char- 



FiG. 91. — sporadotrema cvlindrtcum. . , . . , , 



Photograph of a section through a actcr ot the SpCClCS IS the COlour 



specimen showing the chambers and variety. Some Specimens are 



the thick outer wall perforated bv the -^ -^ 



foramina, x 5 diams. ' dark purplish red, others pmk, 



yellow, or orange coloured. 

 Large specimens are over an inch in height and in expanse, 

 and many specimens just under an inch both ways are to be 

 found in the collections. Although size is not as a rule an 



