imperfectly -hnoivn Species of Stromatoporoids. 11 



perforated tubercles, and which are clearly recognizable in 

 tangential sections. The interlaminar spaces are also wider, 

 and the general tissue is of a coarser type than in 8. eifeliensis, 

 while the ramified tubulation of the skeleton-fibre in the 

 latter is represented by a finely porous structure. Lastly, 8. 

 eifeliensis is an almost constantly encrusting type, while I have 

 never observed a similar habit of growth in 8. granulata. 



Formation and Locality. Not uncommon in the Hamilton 

 formation of Arkona, Outario ; also in the Corniferous Lime- 

 stone of Port Colborne and other localities in Western Ontario. 



Lahechia conforta, Lonsd., sp. 



Monticularia conferta, Lonsdale, in Murchison, Sil. Sjst. p. 688, pi. xvi. 



fig. 5(1839). 

 Lahecheia conferta, Milne-Edwards & Jules Haime, Pol. Foss. des Terr. 



Pal. p. 280 (1851), and Mon. Brit. Foss. Cor. p. 269, pi. Ixii. fi^s. 



6-6 c (1855). 



Coenosteum usually in the form of a laminar expansion of 

 vai'iable thickness, attached by a basal peduncle, and having 

 the rest of the lower surface covered by a concentrically 

 wrinkled epitheca. Upper surface without monticules, covered 

 with prominent, rounded or elongated, often conical tubercles, 

 the apices of which may be imperforate, or which exhibit a 

 minute circular summit-aperture. Often the tubercles become 

 coalescent to a greater or less extent, and give rise to vermi- 

 culate ridges. The surface between the tubercles is smooth, 

 and no astrorhizal grooves are developed. 



In internal structure the coenosteum consists of stout, circu- 

 lar or oval, radial pillars, which have a diameter of ^ to ^ 

 millim., and terminate upwards in pointed extremities, each 

 being traversed by a central canal. The pillars give rise to 

 radiating " arms " or plates, which unite with one another in 

 such a manner that the entire space between the pillars becomes 

 filled with a tissue of calcareous vesicles, the convexities of 

 which are directed upwards. 



Ohs. This well-known species occurs typically in the form 

 of laminar expansions with an epithecate base and peduncle 

 of attachment, but in some instances an encrusting habit of 

 growth is observable. Young examples may be only 2 or 3 

 centim. in diameter, and 1 millim. in thickness ; but old 

 specimens may be of greater size, perhaps a foot in diameter, 

 and may reach a thickness of 2-3 centim. A single specimen 

 often consists of two or more superposed colonies. The sur- 

 face differs from that of many Stromatoporoids in the complete 

 absence of "■ mamelons," and of any indications of an astro- 

 rhizal system^ being covered throughout with prominent 



