350 



THE M0NTICULIP0R0IDS. 



In many Monticuliporoids the surface is studded at intervals with 

 small elevations which are known as "monticules" (fig. 224, a), 

 and which are usually constituted by groups of corallites of larger 

 than the average size. In other cases, there are scattered depressed 

 areas, usually stellate in form, which are occupied by the " meso- 

 pores " only, and which are known as " maculae." These can be 

 shown to be really of the nature of centres of growth for the colony. 



So far as is certainly known, the walls of the tubes in the Monti- 

 culiporoids are wholly destitute of mural pores, or foramina of any 

 kind, the chambers of contiguous tubes being thus completely sep- 

 arated from one another. Considering the vast number of thin 



(■jhF* 



B 



Fig. 228. — a, Part of a typical specimen of Monotrypella pulchella, E. and H., from the Wen- 

 lock Limestone of Dudley, of the natural size ; b, Part of the surface of the same, embracing one 

 of the clusters of large corallites, enlarged. (Original.) 



sections of the Monticuliporoids which have been examined by 

 competent observers, the imperforate condition of the walls of the 

 tubes in the Monticuliporoids must be regarded as free from doubt ; 

 and it constitutes one of the most marked features by which these 

 organisms are separated from the Cyclostomatous Polyzoa. Mural 

 pores have been described by De Koninck, and also by the present 

 writer and Mr R. Etheridge, jun., as occurring in the genus Stenopora; 

 but the exhaustive investigations of Waagen and Wentzel have shown 

 that even in this genus the walls are really imperforate, and that the 

 structures described as pores in such forms as Stenopora Jkackii must 

 admit of a different interpretation. Mr Ulrich has also described 

 pores as occurring in a Monticuliporoid, but it may be suggested 

 with much probability that, in this case, the organism observed is 

 really referable to some other group. 



In almost all the Monticuliporoids the tubes are crossed by trans- 

 verse calcareous partitions or " tabulae," which are in general very 

 numerous (fig. 225, b), though occasionally limited in their develop- 

 ment. Usually, in the dimorphic forms, the autopores have few and 

 remote tabulae, while the mesopores have a much greater abundance 

 of these structures. Mostly, the tabulae are "complete," forming 

 horizontal partitions which extend entirely across the tubes (fig. 



