i82 CORALS 



convex and perforated by minute foramina surrounded by 

 solid imperforate boundaries (Fig. 88, B). There are no 

 pillar pores. The colour is almost invariably of the dark 

 red tint which is technically known as salmon colour. No 

 white varieties have been found. In addition to these 

 characters, which can be observed without dissection, there 

 are other characters of the internal chambers which separate 

 the genus clearly and distinctly from Polytrema. 



The most curious fact about the two genera is perhaps 

 that of their geographical distribution. A very large number 

 of dried corals and shells from various islands of the West 

 Indies and the Western American coasts have been examined, 

 and without exception the red foraminiferan discs attached 

 to them have invariably shown the Homotrema characters.' 



In the Mediterranean Sea Polytrema is very abundant, 

 and Homotrema does not occur. In the tropical Indian and 

 Pacific Oceans both genera occur, and sometimes specimens 

 of the two are found on the same piece of coral, but on the 

 whole Polytrema is the more common. In the New Zealand 

 area Polytrema was found by the Tei'va Nova expedition to 

 be abundant, but no specimens of Homotrema were obtained. 



No specimens of either genus have been found either in 

 the Arctic or Antarctic Seas. 



vSporadotrema. — The third genus of this series of 

 Foraminifera is Sporadotrema, which more fully justifies its 

 place in a book on corals in being larger and more robust 

 than the other two. 



The first specimens of this genus to be discovered were 

 found by Captain Warren in the Gulf of Manaar and were 

 described by Carter under the name Polytrema cylindricum ; 

 but the richest collection of specimens was made by Stanley 

 Gardiner, dredging in water 30-150 fathoms in depth in the 

 Indian Ocean. '^ 



Specimens have also been found in Torres Straits, off the 

 Phihppine Islands, and in the tropical Pacific Ocean. The 



1 Since the above sentence was written one specimen of Polytrema 

 from I^arbadoes has been found. 



- S. J. Hickson, Transactions of the Linnean Society of London, vol. 14, 

 1911. 



