58 THE GENUS MONTICULIPORA. 



on the surface of the Russian Lower Silurian specimens.^ I 

 suppose that these clusters are continuations from the original 

 and larger zooecia, which were budded out round the smooth 

 centra when the colony was in its Ceramopora stage. In some 

 there is seen a sort of ' reversion,' the zooecia on the surface of 

 Montictilipora having again assumed the unmistakable char- 

 acters of Bryozoon, becoming oblique and radiating as in a 

 Ceramopora. Longitudinal sections, however, demonstrate 

 that there is a direct continuation from the tubes of the Monti- 

 culipora into those of the Ceramopora, or that the former again 

 have changed into the latter." 



Havine thus described what he believes to be the mode of 

 development in Monticulipoi^a peiropolitana, Pand., Dr Lind- 

 strom proceeds to give an account of the development of a 

 Silurian fossil which he terms Monticiilipora ostiolata, and which 

 he identifies with the Trematopora ostiolata of Hall (Pal. N.Y., 

 vol. ii, p. 152, PI. XL. fig. 5), with the Nebulipora papillata of 

 M'Coy {M. papillata, E. and H., Brit. Foss. Cor., p. 266, PI. 

 LXIL fig. 4), and with Thecostegites hcmisphcBrictis of Ferd. 

 Roemer (Sil. Faun. Tennessee, p. 25, PL IL figs. 3, 3 a). 

 This form is stated by Dr Lindstrom to commence its existence 

 as a Discoporella, and then to pass into what may be called 

 the '' Fistulipora stage," each cell being now "surrounded by a 

 mass of small vertical, circular, or polygonal tubes having the 

 appearance of a ccenenchyma," and all the tubes, both large 

 and small, being " traversed by tabulae of the same incomplete 

 type as those which characterise Alonticulipora!' ^ From this 

 " Fishilipora stage " the colony is stated to pass next into what 

 Dr Lindstrom calls the " Thecostegites stage," in which the in- 



1 It is probable that Dr Lindstrom is in error in supposing that the Upper Silu- 

 rian specimens to which he here alludes are really identical with M. petropolitana, 

 Pand., as the latter would seem to be really an exclusively Lower Silurian species; 

 but as I have not seen his specimens, I can only express myself on this point with 

 much diffidence. 



2 I do not understand precisely what Dr Lindstrom may mean by " incomplete" 

 tabulce ; but the tabular of almost all the Monticuliporce that I have examined, 

 except AT. frondosa, D'Orb., M. Selwynii, Nich., and certain allied types, are just 

 as " complete " as they are in the typical members of the Favositidcc. 



