786 J. STANLEY GARDINER, 



the dividing walls. All the calices are polygonal with thin edges but may be divided into 

 two classes, (a) those on the top scarcely showing any budding, 10 — 14 mm. in diameter, 

 walls thin edged but 1 — 3 mm. thick at level of columella, septa about 34, alternately larger 

 and smaller, more than two-thirds reaching the columella, each with 6 — 10 low, subequal, 

 blunt, rough teeth, the innermost commonly larger and forming a little crown rising 

 1-5 — 2 mm. above the top of the columella, and (b) those to the sides, vigorously budding, 

 g — 9 mm. in diameter, crowded, more iiTegular, less polygonal, walls thin, at level of columella 

 not more than 1 mm., same depth or even up to 5 mm. (hence appearing very markedly 

 different), septa about the same number alternately larger and smaller, less than two-thirds 

 reaching the columella, with 2 — 7 (commonly 3 or 4) much higher, irregular, very blunt and 

 spiny teeth, those round the pali narrower but not more marked than the rest, though rising 

 to the same height above the columella. 



This extraordinary variation of the calices represents types as distinct as P. abdita and 

 profundicella, or P. sulfurea and quoyi (see Ed. and H.), and throws a considerable light 

 on the variability of the genus. It distinctly suggests that mere size has nothing to do 

 with the number of septa in adult calices. 



Locality. Hulule, reef-flat to south-west. 



63. Prionastraea crassior (Ed. and H.). (PI. LXIV. figs. 45, 46.) Ed. and H., Ii. 



p. 515. 



I refer a specimen about 38 cm. long by 20 cm. high and the same in thickness, and 

 probably having more than 2000 corallites, to this species, with the description of which it 

 corresponds in every particular. 



The colony is a very large, heavy mass, rough and uneven (hilly) on the surface but 

 not in any way gibbous. It is covered with calices, the older of which average between 

 10 and 11 mm. in diameter, with younger ones of 5 — 7 mm. between. On the upper part 

 the calices are more or less polygonal, relatively deep (5 — 6 mm.), thin walled (seldom less 

 than 1 mm. except where a new calice has formed), but on the sides are more rounded or 

 oval, shallower, and much thicker walled (2 — 3 mm.). The septa are continuous over the 

 walls (1 mm. exsert), always slightly thickened, but quite markedly so towards the base of 

 the mass, where, on the top of the walls, they alternate with fine ridges, not generally 

 represented by any trace of septa within the corallites, and rise somewhat at the edges of the 

 calices giving an appearance almost of furrowed walls. The septa number about 25 — 30 in 

 the fully formed calices, approximately equal in size, no cycles distinguishable, often one or 

 tvifo groups of three fusing together, 20 — 24 joining in to the columella which is formed of 

 fine trabeculae from their edges, closely packed together (spongy) in a mass about 1%5 mm. 

 in diameter. The septa are narrow above and fill almost perpendicularly at the edges of 

 the calices ; they are thin and not granulated laterally, and their teeth are relatively low 

 and blunt but increase in size towards the centre, the ring of teeth on the sej)arate septa 

 of the shallower calices simulating a crown of pali. In section the endothecal dissepiments 

 are a little inclined, about "8 mm. apart. The walls of the separate corallites are to a con- 

 siderable extent welded together, but are more rapidly than other parts penetrated by boring 

 organisms, so that they may appear relatively cavernous. 



The colony was attached to the overhanging edge of a lagoon shoal by a nari-ow, dead 

 base, on which part were gi-owing Lithothamnion, Halimeda, red Polytrema, a colonial 



