iambe. J CANADIAN PALAEOZOIC CORALS. 155 



Corallum aggregate, made up of cylindrical stems that proceed upward 

 from an initial, basal corallite and by lateral calicular gemmation form 

 large explanate masses somewhat flat above and irregularly convex 

 below ; the largest specimen seen measuring 23 cent, across and nearly 

 10 cent, high at the centre. Coral] ites touching each other or separ- 

 ated by spaces generally less than their half diameters, usually somewhat 

 flexuous, with not very pronounced annular constrictions and growth- 

 swellings at unequal intervals, furnished with a complete epitheca exhib- 

 iting fine transverse lines and longitudinal septal furrows ; varying in 

 diameter from 5 to 20 mm., with an average diameter of about 15 mm. 

 The young corallites rapidly reach a mature size ; they appear to proceed 

 from expansions or outgrowths of the side of the parent stem that repre- 

 sent lateral extensions of former calyces. Septa about fifty-two in num- 

 ber in average sized corallites, of two sizes, alternating with each other, 

 the larger of which by the union of their inner edges forming a wall that 

 encloses a narrow axial tabulate area as in C repidophyllum colligatum, 

 whilst the shorter are only two-thirds as long. Their sides bear arched 

 carinae that curve upward and inward from the outer wall and appear on 

 the free edges of the septa in the calyx as small transverse teeth. Tabu- 

 late area, cylindrical, varying in diameter from a little less than 2 to 4 

 mm , with frequently a gap in the inner wall indicating the position of the 

 septal fosette. Tabulae flat, horizontal, about six occurring in a space of 

 5 mm. Interseptal spaces, as far inward as the inner edges of the sec- 

 ondary septa, filled with outwardly ascending rows of small vesicles. 

 Calyces shallow, flat at the centre where the upper end of the inner wall 

 is visible, their sides at first rapidly ascending, then spreading horizon- 

 tally at the margin. 



Locality and Jormations. — Abundant in the Hamilton formation of 

 Ontario, less common in the Corniferous limestone of the same province. 



Crepidophyllum colligatum, Billings. (Sp.) 



Plate XIII., figs. 2, 2a, 26. 



Heliophyllum colligatum, 1 'Billings. 1859. Canadian Journal, new series, vol. IV, p. 126. 



" " Nicholson. 1874. Palaeon. of Ont., p. 28, pi, V., figs. 3, 3a. 



Diphyphyllum colligatum, Rominger. 1876. Geol. Sur. Mich., Foss. Corals, p. 126, pi. 

 XXXVIII. , fig. 3. 



Corallum compound, made up of straight, subparallel, cylindrical coral- 

 lites that radiate from a single initial corallite and by rapid gemmation 

 form large explanate masses that attain a breadth of over 30 cent, and a 

 height or thickness of about 23 cent, the upper surface being slightly 

 convex and the basal surface rather flat. Corallites periodically and ab- 



