162 ON THE SOLITARY CORALS, COLLECTED BY DR A. WILLEY. 



almost meet in the centre of the calice, nearly obliterating the axial fossa; their 

 upper edges extend nearly horizontally inwards, while their inner edges slope almost 

 perpendicularly down to the axial fossa. The secondaries do not project so far as 

 the primaries, but are thicker and more exsert than the tertiaries, which are very 

 thin and inconspicuous. 



Extreme height of the largest specimen, 10 mm. Diameter of the calice of same 

 5'5 mm. Depth of the calice from the top of the theca to the edges of the septa 

 in the axial fossa 15 — m 2 mm. 



Loc. Sandal Bay, Lifu ; 40 fathoms. Seven specimens. 



In spirit specimens of this coral the body- wall can be seen to extend for a 

 short distance down the outside of the theca. As the costae do not generally extend 

 below the body-wall, there would seem to be an epitheca deposited by it completely 

 obliterating them and filling up their intercostal spaces. In one specimen, which has 

 been much overgrown by a sponge, the edge of such an epitheca is distinctly 

 visible, the body-wall having evidently been forced to withdraw itself higher up the 

 corallite. 



In the two youngest specimens, which are about 5 mm. in height, the shape of 

 the calice is nearly hexagonal. The three cycles of septa are fully developed, but all 

 are very slightly and equally exsert. 



GENUS. Rhizotrochus, Milne-Edwards and Haime. 



■2. Rhizotrochus levidensis, n. sp. (Fig. 2.) 



The corallum is conical and covered by a well developed stout concentrically 

 marked epitheca. There is usually one large radicle with two or three smaller, 

 hollow roots, arising as if from its sides. There are no costae, or costal prominences 

 of the epitheca. 



The calice is slightly oval and deep; the wall is formed entirely of the epitheca, 

 no visible theca being present. The septa are not at all exsert, of moderate thickness 

 and entire; their sides are covered with coarse pointed spines. Three distinct cycles 

 in six systems are present. The primaries are much the most conspicuous and meet 

 at the bottom of the very deep, slightly elongated central axial fossa. Slightly below 

 the edge of the epitheca the primaries and secondaries project for some distance 

 nearly horizontally into the calice, ending almost perpendicularly by the axial fossa. 

 Of the primaries two, situated at opposite ends of the axial fossa, are distinctly 

 smaller and slope more gradually inwards than the four at its sides. The tertiaries 

 are very small and narrow, not being more than half as broad as the secondaries. 



Extreme height of the largest specimen, 12 mm. Long diameter of the calice of 

 same, 6 mm. ; short diameter, 4"6 mm. 



Loc. Sandal Bay, Lifu ; 40 fathoms. Three specimens. 



The two smaller specimens have the calice rather more circular than the largest, 

 whose dimensions are given above. The species is evidently very closely allied to 

 Rhizotrochus affimis (Duncan), but separated by its smaller size, more circular form 

 and the presence of only three cycles of septa. 



