150 MARINE INVERTEBRATES 
M. palmata. 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. danaé. 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 ALCYONARIA or HALCYONOIDA 
In this subclass—the 
actinoid corals—the pol- 
yps are of two kinds. 
The smaller are without 
tentacles and are called 
siphonozodids. The 
larger have but eight 
radial partitions and 
eight tentacles. This 
limitationof 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. haleyonoids. 
