98 



CORALS 



membcis of this family in some important particulars, and 

 it is possible that when we have a more extended knowledge 

 of its anatomy it may have to be considered as the type 

 genus of a separate family. 



The name is derived from the shape assumed by the 

 most common variety or species of the genus, which is that 

 of a large shallow bowl attached by a thick stem to the 

 rock. The genus is widely distributed in shallow water in 

 the Indian and Pacific Oceans, but does not occur in the 

 West Indian waters. 



It seems to be a characteristic feature of the genus that 



in the early stages of its growth 

 it has a shape like a mushroom 

 with a flat or slightly concave 

 disc and a ring of calices round 

 the margin (Fig. 40).^ By mar- 

 ginal growth, these calices become 

 situated on the upper side of the 

 disc, and are succeeded by others 

 that are formed on the growing 

 edge. This process is continued 

 until the bowl shape is attained 



(Fig- 41)- 



The other varieties of form 

 assumed by the adult corallum 

 seem to be due to irregularities 

 in the growth of the margin, and 

 thus great sheets of Turbinaria are formed with fringed 

 or foliate edges, plates, or dishes which seem to have lost 

 the original stalk and form encrusting laminae over the rock 

 or over other laminae of the same coral. Colonies of this 

 genus which ramify in the manner of the Madrepore and 

 other corals, are not common, but do occasionalh' occur. 

 The corals of this genus also reach great dimensions. A 

 specimen in the British Museum of irregular shape with a 

 boundary of 16 ft. 8 in. is 1500 lbs. in weight. - 



The upper surface of the corallum is provided with a 



^ Pace, /. I.itnt. Soc. .x.wiii. p. ^6i. 

 2 F. J. BelC J.n. Micr. Soc. 1S95, p. 148. 



Fig. 40. — Turbinaria. A young 

 stage in the dc\-elopnu-nt of a 

 colonv. Xat. size. 



