150 



MARINE INVERTEBRATES 



M. paltnata. This madrepore grows like the one described above, 

 except that the branches do not remain separated, but unite or grow 

 together, giving broad, flat surfaces which resemble fronds. When 

 carefully examined these surfaces show striations which indicate the 

 course of the branches. The strictures forming the lobes are caused by 

 the failure of the branches to unite. On the Carysfort Reef of the 

 Florida Keys this species covers the top of the reef for several miles, 

 nearly reaching the surface, and appears like a vast bed of low yellow 

 shrubbery. (Plate XLV. ) 



GENUS Astrangia 



A. danae. A small coral found on the New England coast. It lives 

 in the clefts of rocks in small patches, sometimes two to three inches 

 across and one quarter of an inch or more high. Frequently it is like a 

 thin crust of lime covered with star-like divisions. Sometimes it forms 

 branches. The living animals are white, and when expanded rise above 

 the cells and resemble a cluster of small sea-anemones. 



SUBCLASS ALCYONAEIA or HALCYONOIDA 



In this subclass the 

 actinoid corals the pol- 

 yps are of two kinds. 

 The smaller are without 

 tentacles and are called 

 siplionozooids. The 



larger have but eight 

 radial partitions and 

 eight tentacles. This 

 limitation of partsplaces 

 them in a higher rank 

 than the corals of the 

 first subclass. Another 

 characteristic of these 

 polyps is the presence 

 of symmetrical branch- 

 lets on the tentacles, 

 which give them a 

 feather-like appearance. 

 These corals are called 



Alcyonium palmatum : A^ entire colony ; B, spicules 



