8 Mr. II. M. Bernard on the 



cups may be distinguishable. For instance, the development 

 of exsert laminate septa may lift the cups above one another 

 (see PI. I. figs. 3, 11, 12). 



Fig. 3 refers to Montlivaltia, of especial interest because it 

 was the irregular bands of epitheca round specimens of this 

 genus which induced Dr. Gregory to give up this element of 

 the coral skeleton in despair. We shall now show that an 

 understanding of these bands is essential to a true insight 

 into the morphology of the skeleton. 



It is frequently stated * that in Montlivaltia there is 

 epitheca, but no theca. There was, however, certainly a 

 prototheca, and examination of the coral shows that the 

 successive protothecaj gradually flattened out until, after 

 reaching a certain size, they formed a series of flat saucers 

 (rig. 3, e, e, e . . .) of nearly uniform size, and piled up one 

 above the other as tabular with edges which may either only 

 just reach the surface or be bent sharply upwards to varying 

 heights according to the accidents of secretion. On the left 

 of the figure a few of the septa are shown supporting and 

 raising the successive saucers above one another. The septa 

 of each polyp continue those of that which went before it, so 

 that these radial structures naturally run up continuously 

 through the whole skeleton. On the left of the diagram the 

 saucers alone are shown in optical section as a series of flat or 

 wavy floors with turned-up rims. 



Here, then, we have the three facts necessary for the 

 understanding of the case in hand : — 



1. A series of shallow thecae or protothecal saucers ending 

 abruptly at the surface or with edges bent up externally. 



2. The septa which, being exsert, support and lift these 

 saucers above one another, so that, while the septa are con- 

 tinuous, the rims of the cups may be free and separate, or, 

 when bent up, may run together as irregular epithecal bands. 



3. Ihe extreme irregularity of the bands is due to the want 

 of uniformity in the height to which the secretion of the rims 

 of the saucers, if bent up, extends. 



These three factors fully explain the puzzle presented by 

 the epitheca of Montlivaltia. 



It is obvious that in diagram fig. 3 the saucers might 

 contain not single polyps, but gradually expanding colonies 



* E. (/., by Miss Ogilvie (/. c. p. 158), who, however, followed Milne- 

 Edwards and Haime, who wrote with reference to Ample.ius, in which 

 the succession of saucer-shaped prctothecte is very pronounced :— 

 '* Quelquefois meme la muraille parail manquer et le polypier nest 

 constitue que par une serie cle cornets ties ivases et naissant les uns 

 au-dessus des autres" (Ann. Sci. nat. (3 e ) ix. p. 84, 1848). 



