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FAMILY III.— TURBINOLIAD^E. 



In this, and all the families which have now to come 

 under consideration, the tissues secrete calcareous matter, 

 which unites into a solid internal skeleton of stone, known 

 as the CORALLUM. The stony substance is chiefly deposited 

 — 1. in the integuments of the base and column, forming 

 the wall (murzis) ; 2. in the septa, forming a series of 

 perpendicular plates (lamellce), which radiate inward from 

 the wall ; and, in some cases, another circle, or circles, of 

 similar plates, palules {pali), which do not reach the 

 wall ; and 3. (as I believe) in the ovarian mesenteries, form- 

 ing a series of plates, generally twisted, in the bottom of 

 the cavity, called the columella. The hollow centre, 

 formed by the upper edges of the plates, is called the 

 calice [calyx). Sometimes the exterior of the wall is 

 furnished with longitudinal ribs (costce), which correspond 

 to the plates. 



The plates are arranged in cycles : those of the first 

 cycle project furthest inwards ; those of the second bisect 

 the interspaces ; those of the third bisect the interspaces 

 thus formed, and so on. The whole of the plates developed 

 in one primary interspace constitutes a SYSTEM. 



In the Turbinoliadjs the corallum is solid (not porous), 

 simple, with the lamellar interspaces reaching to the 

 bottom of the cavity, and perfectly free. The plates are 

 highly developed, simple, and generally have a granular 

 surface. The ribs are well-marked. 



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