uuiBE.] CANADIAN PALAEOZOIC CORALS. 187 



Calyx with rapidly expanding horizontal or reflexed margins surrounding 

 a steep-sided central pit at the bottom of which is a rounded boss show- 

 ing the convergence of the inner ends of the septa ; depth nearly one 

 half its width, Septa as seen in the calyx, radiating outward with little 

 or no incipient twisting, sharp-edged at first and when ascending the 

 steep sides of the central pit but developing on the expanded margin into 

 low convex ridges about 1 mm. broad at the periphery where they are of 

 nearly equal size although elsewhere they show a differentiation into alter- 

 nating primaries and secondaries most noticeable on the side of the pit. 

 The rapidly increasing area of the calyx outside the pit necessitates the 

 addition of new septal ribs which are supplied by intercalation or by the 

 bifurcation or trifurcation of the old ones. 



An inner axial area, showing in the bottom of the calyx of the tppe 

 specimen as a rounded projection, is formed by the presence of narrow 

 tabulte, turned down at the edges, over which the septa pass, either 

 meeting at a point or not continued quite so far, so as to leave a small, 

 smooth, central space, 3 or 4 mm. in diameter. Outside the tabulate area is 

 a broad zone of arched plates, of unequal but rather large size, that fill the 

 spaces between and support the periodic calycinal expansions. Strength- 

 ening acanthiform growths developed from the under, concave surface 

 of the arched plates are noticed in many places. Septa, in the type specimen, 

 numbering about ninety, thin, apparently carinated on their side faces, of 

 two alternating sizes, the larger passing almost to the centre, the shorter 

 not encroaching on the tabulae, their vertical continuity interfered with by 

 the vesicles as the periphery is approached ; represented on the calycinal 

 margins by the low septal ridges. 



Locality. — Grand Manitoulin Island, Lake Huron, collected in 1865 

 by R. Bell and H , S. Vennor ; Clinton formation. 



Chonophyllum nymphale, Billings. (Sp.) 



Plate XVIII., figs. 1, la. 



Cyathophyllum nymphale, Billings. 1862. Palaeoz. Foss., vol. I., p. 111. 

 Qhonophyllum nymphale, Lambe. 1899. Ottawa Naturalist, vol. XII. , p. 251. 



11 Corallum simple, short, broadly expanded, concave on the lower 

 surface, convex above ; dimensions of the type and only specimen 

 known, height at centre 4 cent., breadth about 9 cent. Basal surface 

 apparently provided with an epitheca. Calyx shallow, convex at the 

 centre, with broadly expanding reflexed margins exhibiting about eighty 

 low, rounded septal ribs that increase in breadth outwardly. In a 

 radial section a central area, about 1 cent., in breadth, is disclosed ; it 



