ASTRiEOPOR^ GLOBULARES. 97 



masses arc to be rolled over, while the living layer at the surface is always creeping 

 downwards. It is thus not only quite possible, but very probable, that a recently detached 

 specimen might, wlien found, have its point of attachment completely grown over. 



a. Great Barrier Reef, Saville-Kent Coll. 92. 12. 1. 418. 



Species 12. Astraopora ovalis. (PI. XXX. ; PI. XXXIII. fig. 17.) 



Description. — Corallum, seen from above, symmetrically egg-shaped, but flattened on its 

 lower side. The living layer almost meets on the under surface, so that the corallum appears 

 to be free and unattached. The epitheca appears under the edges of the enveloping layer of 

 living coral. 



Calicles crowded, very large and conspicuous, circular, 3 mm. in diameter, projecting witli 

 irregidar margins, one side often thick and reticular, the other thin and membranous. In the 

 thicker portions of the margins, the primitive radial symmetry of the costre is comidetely 

 obscured. Three cycles of septa appear at the margin, the primary being from the first 

 distinct, and, deep down, projecting so as to appear to meet in the centre. 



Young calicles appear in the bottoms of the depressions between the large calicles, as 

 irregular holes in the reticulum. 



The ccenenchyma shows striking variations ; it is coarsely reticular on the uppermost 

 parts of the corallum, but on the sides and under surfaces, the interstices are almost smooth 

 synapticular floors, conspicuous on account of their comparative freedom from echinula; or 

 pores. The calicles projecting above these smooth floors are often waUed round by 

 membranous rings. 



This unique specimen (pre\iously labelled A. lyulvinaria, Lamarck, which it certainly 

 cannot be) is interesting, because it shows an extreme of the globular method of growth. 

 The \\x\x\g coral almost completely envelops it. It lies free, but is hindered from rolling by 

 its flattened under surface. Its almost perfect sjTumetry of form, and its conspicuous calicles 

 distinguish it completely from all the other specimens in the Collection. Further, the 

 contrast between the open reticulum of the upper portions of the coralhim, and the smooth, 

 continuous synapticular floors at tlie sides and lower portions, is more strikuig than in any 

 other form. It is diflicult to avoid suggesting that the continuous concentric floors in the 

 parts where they are developed (viz. sides and under surface) are physiologically adaptations 

 to restrain the free flomng of the nutrient fluids, under the action of gravitation ; such a 

 flowing would tend to destroy the symmetry which we assume to be typical of the species. 



a- Locality not recorded. (T}Te-) 



Species 13. Astraeopora kenti. (PI. XXX. ; PL XXXIII. fig. 19.) 



DcscrijAion. — Corallum irregularly hemispherical, the living layer covering a previous 

 growth like a cap ; epitheca obscured. 



Calicles crowded, small, 2 mm., protuberant, tliin walled, and about 2 mm. high ou 

 uppermost portions of the corallum, but thick walled, papilliform, and 3 to 4 mm. liigh on the 







