68 MADREPORAEIA. 



Species 52. Turbinaria globularis. (PI. XX. ; PI. XXXII. fig. 20.) 



Description. — Corallum an almost glolnilar mass, the growing edges hanging down over 

 and creeping round the dead remains of former growths of the same colony. 



Calicles protuberant as thick truncated cones, showing no regularity in size and height, 

 some of the larger and older being 5 mm. in diameter of the circular tops, and 6 mm. high. 

 Calicles show secondary budding from their sides, the smallest buds are mere points on the 

 lateral slopes of the cones or at their bases. The aperture occupies the whole summit of the 

 projection. The septa vary from 10 in the minute buds to 42 in the larger calicles. They 

 are closely arranged, thin, and reach nearly to the half-radius circle. They are very regular 

 in the medium-sized calicles, but irregular in the largest. Slanting down from the margins, 

 they descend suddenly round an oval, cylindrical, or bowl-shaped fossa, which is often deep or 

 else partially filled by a protuberant, often globular, spongy columella. 



Interseptal loculi slit-like, petaloid. 



Coenenchyma rather coarsely reticulate, slightly echinulate, with vertical ridge-and-furrow 

 system on the sides of the protuberant calicles. 



There are two specimens grouped under this heading, the type being an ovoid mass 

 20 cm. long by 16 across, from Diego Garcia, and the other a nodule 9 cm. long, from Palm 

 Island, Great Barrier Pieef, which differs from the type in having much smaller calicles. The 

 substratum in the larger specimen shows signs of being composed of various earlier growths of 

 the same stock. 



There are two interesting characters presented by these specimens : (1) adventitious 

 budding appears to be the rule, and must be regarded as a return to earlier methods, from the 

 more specialised type of budding of the genus. (2) the calicles protrude, whereas in the 

 glomerate growth they are typically immersed by the rapidly thickening coenenchyma. Tliis 

 is clearly to be taken in connection with the adventitious budding, which would allow a 

 certain numljer of polyps, as it were, to get the start of the ccenenchyma. 



There is unfortunately no good section to show the exact relations of the adventitious 

 budding to the specialised Turbiuarian method. The adventitious budding probably only 

 takes place at the very thickest portions. The smaller of the two specimens illustrates the 

 conditions very well. One half of the nodule is of no great thickness and the calicles are of 

 nearly equal size, hardly protuberant and scattered, new calicles appearing along the growing 

 edge; the other, half, however, which is thick and solid, is closely beset with large projecting 

 calicles interspersed with minute buds. It looks as if the adventitious budding were a safe- 

 guard against complete submergence of the calicles by the coenenchyma, this being a 

 phenomenon discoverable in other cases of threatened submergence. 



It is worth noting that the very possibility of explaining the different features of these 

 corals by the physical conditions of growth, however gratifying it may be in itself, tends at 

 the same time to shake one's confidence in their value as taxonomic characters. 



a. Diego Garcia. G- C. Bourne, Esq. (Type.) 



h. Palm Island, Great Barrier Eeef. Saville-Kent Coll. 



