LAMBE.l CANADIAN PALEOZOIC CORALS. 183 



the surface in radially septate calyces with narrow, sunken confluent mar- 

 gins and broad cone-shaped central prominences enclosing deeply exca- 

 vated pits that are from 1 to nearly 2 cent, apart and vary in width from 

 5 to 7 mm. The septa average thirty-six in number, are alternately long 

 and short in the pits, half passing to the centre, the others terminating 

 in the vertical pit sides ; the differentiation in the size of the septa is 

 apparent at times on the outer descending slopes of the central projections 

 but is lost on the sunken marginal floors where the septal ridges attain 

 a maximum breadth of nearly 1 mm. The presence of septal pore-openings 

 has not been detected. Other structural details as described in former 

 species. 



From A. diffluens this species differs principally in its much more 

 robust growth, in the greater size of the calycinal pits, and in the propor- 

 tionately larger mammiform cones. 



Formation. — Niagara. 



Arachnophyllum diffluens, Milne-Edwards and Haime. (Sp.) 

 Plate XIV., fig. 12. 



Strombodes diffluens, Milne-Edwards and Haime. 1851. Polyp. Foss. desTerr. Palaeoz., 

 p. 431. 

 " " Milne-Edwards and Haime. 1855. Brit. Foss. Corals, p. 294, pi. 



LXXL, figs. 2, 2a. 



Billings. 1866. Cat. Sil. Foss. of Anticosti, p. 34. 

 Strombodes pigmceus, Rominger. 1876. Geol. Sur. Mich., Foss. Corals, p. 131, pi. 



XLVIIL, fig. 3. 

 Arachnophyllum diffluens, Lambe. 1899. Ottawa Naturalist, vol. XII., p. 244. 



"Coralluin forming laminar or discoidal expansions, composed of confluent 

 corallites whose calyces open on the surface with scarcely any line of demar- 

 cation between them ; reaching a breadth of 9 cent, and a thickness of 

 between 2 and 3 cent. Calyces, varying in width from 8 to 12 mm., flat 

 or shallowly concave in the marginal area, with a circular, elevated rim 

 surrounding a central pit 3 or 4 mm. in diameter from which radiate the 

 septa as narrow convex ribs having a maximum breadth of about 5 mm. 

 The elevated rims surrounding the pits stand, in some specimens, much 

 more prominently above the surrounding, sunken, calycinal extensions 

 than in others, whilst at times they develop into salient, conical projec- 

 tions with the pit forming an excavation at the top. Lateral junction 

 of contiguous calyces sometimes very slightly raised, more often seen as 

 a plane surface in which no dividing line is apparent. Septa averaging 

 thirty in number as in other species of the genus, lamellar and continuous 

 vertically in the vicinity of the central pit, converted on the flat calicinal 

 margin into surface ribs that join those of neighbouring calyces ; of two 



