S Mr. H. M. Boniard on the 



cups may be distinguishable. For instance, the development 

 of exsert laminate septa may lift the cups above one another 

 (see PL I. figs. 3, 11, 12). ' 



Fig. o refers to Month'valda, of especial interest because it 

 uas the irregular bands of epitheca round specimens of this 

 genus A\ hich induced Dr. Gregory to give up this element of 

 the coral skeleton in despair. We sliall 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 MontUvaJtia there is 

 epitheca, but no theca. There was, however, certainl}^ a 

 prototheca, and examination of the coral shows that the 

 successive prototheca^ gradually flattened out until, after 

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

 (tig. 3, f, 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 lett 

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

 raising the successive saucers above one another. The septa 

 of each pol} p 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 turued-up rims. 



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

 understanding of the case in hand : — 



1. A series of shallow thecte or protothecal saucers ending 

 abruptly at the surface or with edges bent up externally. 



2. 1 he 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 tlie saucers, if bent up, extends. 



These three factors fully explain the puzzle presented by 

 the epitheca of MontUvaltia. 



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

 contain not single polyps, but gradually expanding colonies 



* -£"• il; ty 3[iss Ogilvie {I. c. p. 158), wlio, however, followed Milue- 

 Edwards aud Haime, -who wrote with refereuce to Amplci-us, iu which 

 the succession of saucer-shaped protothecfe is very prouounced : — 

 " Quelquelbis meme la nmraille paiait niauquer et le polvpier ii'est 

 constitue que par une serie de cornets ties erases et naissaut les uus 

 au-dessus dcs aulres " (Ann. fcici. nat. (o^) ix. p. 8-i, 1848). 



