294 TABULATE CORALS. 



They are usually to some extent contiguous ; but they are 

 always partially separated by the corallites of the smaller series, 

 which are also subpolygonal or rounded, and more or less 

 thickened towards their mouths. Sometimes (as in M. fron- 

 dosa, D'Orb., M\ tumida, Phill., &c.) many of the smaller 

 corallites become abnormally thickened, so as to constitute a 

 third series, in which tabulae do not appear to be developed, 

 and which present themselves on the surface as a series of 

 blunt spines. In other cases whether or not spiniform coral- 

 lites are present the small corallites are more closely tabulate 

 than the larger ones, and are thus easily recognised in longi- 

 tudinal sections (PI. XIII., figs, i b and 2 a). The general 

 characters of the Monticuliporcz of this section will be best 

 understood from the following very brief descriptions of M. 

 mammulata, D'Orb., and M. ramosa, D'Orb. 



Monticulipora (Heterotrypa) mammulata, D'Orb. 

 (PI. XIII. , figs, i - 1 b.) 



Monticulipora mammulata, D'Orbigny, Prodr. de Paldont., t. i. p. 25, 1850. 

 Cfuztetes mammulatus, Edwards and Haime, Pol. Foss. des Terr. Pal., p. 267, 



PI. XIX., fig. i, 1851. 

 Monticulipora mammulata, Edwards and Haime, Brit. Foss. Cor., p. 265, 



1854- 

 Chcetetes mammulatus, Nicholson, Quart. Journ. Geol. Soc., vol. xxx. p. 508, 



PL XXX., figs. 3 - 3 a, 1874 ; and Pal. of Ohio, vol. ii. p. 207, 1875. 



Spec. Char. Corallum in the form of thin undulated expan- 

 sions, from two to four lines in thickness, consisting of two 

 layers of corallites, which diverge from an imaginary central 

 plane, to open on both sides of the frond. Surface covered 

 with well-marked " mamelons " placed at intervals of from half 

 a line to a line, and composed of corallites, which may be 

 slightly larger than the average, and which sometimes have 

 their calices closed by a calcareous membrane. Large or 

 average corallites polygonal, their walls but slightly thickened 

 towards their mouths, from eight to ten occupying the space of 

 one line. Small tubes not very numerous, wedged in among 



