MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 577 



Genus MAN1CINA Ehrenberg." 



Polyps verrucose, incompletely separated, forming broad, continuous and sinuous discal and columnar 

 systems, and giving rise to small, massive, elongated or subhemispherical colonies; attached when 

 young by a conical pedicle, but afterwards free with a subcorneal or nearly flat base. Column wall 

 distinct throughout in young, later partly united along the apex of broad inturned collines; in 

 retraction may fold over the tentacles and cover the marginal area of the disk; no sphincter. Perithecal 

 continuation of the gastro-coslomic cavity and mesenteries; proportionately more in young. Tentacles 

 in three or four irregular, alternating, entacmseous cycles, entoccelic and exoccelic, short, introvertible, 

 rounded or knobbed terminally, surface of stem with oval urticating areas. Oral apertures numerous, 

 variable in size. Stomodseal walls deeply ridged. 



Mesenteries hexamerous and regularly multicyclic in young, with two pairs of directives; later, in 

 irregular, multicyclic, stomodaeal systems without additional directives; all filamentiferous; increase in 

 regular hexamerous cycles in young, but irregularly by unilateral pairs later. 



Mesenteries and filaments protrusible. Septal invaginations mainly entoccelic, regularly multicyclic 

 in young, more irregular later. 



Asexual reproduction by continuous stomodaeal fission. Polyps monoecious, viviparous. 



Example. — Mxmicina areolata (Linn.). 



MANICINA AREOLATA (Linnaeus). 



(Pis-. XVIII, XIX, tigs. 129-137.) 



External characters. — Isolated colonies of all sizes;, from 2 to 9 or 10 cm. in length, are 

 met with in shallow water all round the coast of -Jamaica; while from somewhat deeper regions 

 examples have been obtained as much as 20 cm. across. Young specimens are attached by a 

 small base to some pebble, coral, or shell, but older specimens are free. In their carl}' condition 

 the colonies are somewhat crateriform, but soon become elongated and strongly sinuous, very 

 deep bays and convexities being formed along what might be regarded as the primary axis. 

 Circular forms are sometimes found. When young the axial line joining all the oral apertures 

 may be nearly straight, but later is strongly indented. The. discal areas are nearly always 

 continuous, rarely separated by a transverse division, and are often arranged in parallel rows. 



The column wall extends over the thecal edge as far as the base in young polyps, but less so 

 as the colony enlarges. In older specimens it may extend for about 5 mm. down the theca, the 

 remaining naked portion of the corallum being coated with a thin epitheca, to which small 

 molluscs, worm tubes, etc., adhere. In the retracted, or even partly retracted, condition, the 

 column wall extends within the calice for some distance. It is incapable of completely closing 

 over the disk on full retraction, but folds over the, tentacles. During full distension the polyp 

 may extend upward for a centimeter or more beyond the corallum. 



The column wall is strongly ridged, in alternate broad and narrow areas, the former only 

 corresponding with septa. The ridges bear closely arranged verruca 1 , slightly thicker and 

 differently colored from the rest of the wall. The apex of the broader areas is often prolonged 

 a little, almost recalling the acrorhagi of certain anemones. 



During retraction the edge-zone adheres closely to the skeleton, the echinulations of the 

 costse showing through; but on full expansion the wall becomes raised some distance above the 

 corallum. and is then practically smooth, the verruca? being represented by small opaque spots. 



The tentacular zone constitutes a distinct boundary between the column wall and disk, 

 and is comparatively broad on full expansion of the polyp. Three or four alternating cycles of 

 short, stout tentacles occur in young polyps, the members of the innermost cycle being about 5 

 mm. in length. The alternations, however, are rarely regular; smaller tentacles may mingle with 



« "Colony massive, free or pedunculate, broad-based, subhemispherical, tall, and convex or subcorneal or short. 

 Corallites with their walls fused with those of their neighbi irs, except in young forms. Calicinal valleys long, broad 

 and deep, united by simple or broad and furrowed collines. Calices with indistinct centres. Columella spongy, 

 essential. Septa close, thin, strongly granulated laterally, the principal with a paliform lobe, and with the free 

 edge divided by fine teeth, which are regular, close, and largest near the columella. The common plateau is 

 furnished with costae, which are delicate ami dentate, and are partly covered by an epitheca, which is readily 

 detached. Endotheca abundant, unequal." (Duncan, lssj, p. 88. ) 



