A, E. Yerrill — Bermiidian and West Indian Reef Corals. VS 



The chariictors of the septa and eosta? are also variable, though 

 more reliable than the form of the ridges. The septa are not very 

 crowded, though more so than in M. cerebrum. Smaller, thin ones 

 alternate with the larger and usually extend down below the pali- 

 form lobe. The larger septa are rather broad, genei-ally with the 

 inner edge perpendicular, and often sometimes broader above, 

 usually with the summit broadly rounded and continued into promi- 

 nent costa? which have rather regular conical or spiniform serrations 

 on their edges. The paliform lobe is generally well developed and 

 roughly serrulate; the inner edge of the septa bears numerous, small, 

 close, irregular, elongated teeth, many of which are rough or forked 

 at the tip ; those toward the summit are longer, directed strongly 

 obliquely upward and frequently incurved ; those on the rounded 

 summit are usually more regular and divergent. The sides of the 

 larger septa are covered with rather few and scattered conical 

 grains, — much fewer and smaller than in M. cerebrum. 



The columella is variable, but usually well developed, composed of 

 curled lamellose processes, and thickened at the centers. Some- 

 times it is larger and nearly solid or subvesicular. 



In transverse section the walls vary in breadth, but are usually 

 thick and solid. In those specimens that have thin and simple walls 

 at the surface, a section made an inch or so from the surface usually 

 shows most of the walls as thick as usual (about 3 to 5"*"'). The 

 septa in section are thin and sparingly spinulose laterally, quite unlike 

 those of M. cerebrum in similar sections. 



The actinal grooves var^^ considerably in breadth and depth, but 

 they are always decidedly narrower and shallower than those of 

 typical 31. cerebrum, and have a more square-cut appearance. The 

 breadth from wall to wall, at top, is generally 5 to 10'""' ; of the 

 open valley, septal edge to septal edge, 4 to 6™°^ ; depth, mostly 4 to 

 gram Number of septa to a centimeter, usually 14 to 16. One 

 variety [comjiacta) has unusually shallow and narrow vallej^s (8-5™"' 

 wide), with crowded septa. 



This species is the largest and most important of the Bermu- 

 dian reef corals. It occurs abundantly on the inner reefs of 

 Great Sound, Castle Harbor, etc., often close to the shores and in 

 water only two feet deep at low-tide, and mostly in less than twenty 

 feet. It is still more abundant on the outer reefs. It does not occur 

 in Harrington Sound, probabh^ owing to a slightly diminished salin- 

 ity of the water, due to its nearly land-locked condition. It may 

 form masses to 8 feet in diameter and height. 



It is found on the Florida reefs and throughout the West Indies. 



