200 MADREPORARIA. 
coral. Above, the mass is a cluster of large, smooth, rounded knobs, up to 4 em. across and 
4 cm. high, slightly flat-topped, and, as they only swell gradually, with steep sides. Between 
these knobs flat spaces of dead coral are seen, and sometimes openings into the heart of 
the stock. Though the living layer of the uppermost knobs is only some 4 cm. deep, at the 
sides it may be 12-13 em., and even bend sharply 2 em. under the edge. | 
The calicles are 1 mm. in diameter, neatly circular, shallow, but very distinct. The walls 
are conspicuous but low, thin, and often only thickened in the angles sufficiently to make the 
calicles circular. At the thinnest seen from above they are single, rough, uneven threads, and 
are thickened by a tangle of similar threads as an irregular reticulum. In the lower parts of 
the stock these irregularities in the threads swell into rough granules. The septa are also thin 
and rough and symmetrically arranged, but their top edges are very ragged and incomplete. 
The pali are very faintly developed in the calicles on the flat tops of the knobs where the 
elements are specially thin, but down the sides they rise as small rods, themselves insignificant, 
but together forming a raised ring visible to the naked eye (Pl. XXX. fig. 5). The full number, 
eight, is usually present. On the lower parts of the stock the skeleton is all more granular, 
and the intra-calicular skeleton may be but an arrangement of rough granules. The central 
tubercle is often flattened. The columellar tangle seems to be very large, the roughness of 
the septa growing out into synapticule even close up against the wall. 
The section shows’a delicate texture with very thin skeletal elements, the trabecul being 
arranged sheaf-like in a section through a knob, The colour is a light buff or brown. 
This is the description of a very large specimen, 30 cm. across and 20 em. high. In 
growth-form it is somewhat like that described under the next heading, but the knob formation 
is bolder and the calicles are different. It is possible, however, to connect the two specimens 
by assuming that in No. 5 the trabecular elements are laminate and of more rapid growth. 
There are two younger specimens, 0, c, both showing the same type of calicle. In / the 
calicles show hardly any difference from those of a, but its growth is peculiarly interesting. 
Its dead pear-shaped stalk narrows smoothly towards where it was broken off, showing its 
earliest growth like one of the knobs seen on the top of a, of the same size and shape. Later 
growth has swelled this into a flattened mass, 12 cm. in diameter, and with thick rim, and 
with a convex, convoluted top, 9-10 em. high above its thick projecting rim. The con- 
volutions admit of being resolved into a cluster of fused knobs like that of its very earliest 
growth, and now seen rising all over the upper surface of a. 
_ Ine, while the growth-form is somewhat like that of 5, the calicles, though of the same 
type and texture, have very high walls, and thus form a transition between those of a and 
those of the next form, No. 5. The growth-form of ¢ is a convex mass with bold wavy surface, 
and growing on the under surface of a similar mass which had been turned completely over. 
a. Old stock. Zool. Dept. 1904, 10. 17. 46. 
b, c. Young stocks, Zool. Dept. 1904. 13. 17. 47 and 48. 
