JOXES— ON NATURAL HISTORY OF THE BERMUDAS. 9 



hriformis) . Ao-ain in the rock pools an astroicl form Siderastrcea 

 radians is more common than any other, and appears to thrive 

 well, although as before stated the temperature of the water of 

 these tidal pools must be low at times. 



The barrier reef forms a perfect belt all around the islands, 

 Tunning along the southern shore of the group at a distance of 

 less than half a mile ; while, on the northern shore it is distant 

 some twelve miles. At the lowest tides this reef shows in 

 places above the breakers, and presents a mass of corals, 

 gorgouias, and sea weeds, with the exception of certain patches 

 grown over and rendered imperishable by iucrusting serpulse 

 and nullipores. 



In regard to the growth of the Bermuda reefs I cannot 

 acquiesce in the opinion of some naturalists, that all coral reefs 

 require a very lengthened period to grow in. It is doubtless 

 true that some species of polyps secrete their calcareous frame- 

 work slowly, but there are others such as the Millepora alcicornis 

 and Oculina diffusa which personal observation allows me to 

 establish as instances of rapid growth, and as the Millepora in 

 question is by far the most common form on the Bermuda reefs, 

 and which in many parts are almost entirely composed of it, we 

 may conclude that these barrier reefs at least, present an 

 example of a more I'apid development than is usually granted to 

 such formations. 



The reef building corals proper may be said to comprise eight 

 species, yet there is another smaller form, My cedium fragile, 

 which is by no means uncommon, and contributes to the general 

 mass, and on close investigation I have little doubt but that 

 other minor forms may be found. 



I am indebted to Professor Verrill, of Yale College, New- 

 haven, United States, for identifying several species. 



Or. ZOANTHARIA. 



Fam. AsTREiD^. 



Gen. Isophyllia. 



Isophi/lUa dipsacea, Dana. 



This mav be considered the most common coral on the reefs 

 2 



