34 CONTRIBUTIONS TO CANADIAN PALAEONTOLOGY. 



distance apart variable, depending on the amount of thickening of the 

 walls of the corallites at the surface, but generally less than their width. 

 In parts of the corallum, possibly where the regularity of growth has been 

 disturbed, the calyces are nearly or quite at right angles to the surface 

 and irregular in shape, with rounded outlines and without a lip. Often on 

 one side of the expansion, as in Cladopora turgida, Rominger, the out- 

 lines of the calyces are less sharply denned and more depressed than on 

 the other, the difference in the two sides resulting possibly from the 

 corallum not growing quite erect, the side on which the more sharply 

 defined calyces are being probably uppermost. The calyces are frequently 

 closed by opercula. Mural pores of moderate size, about 1 mm. apart 

 vertically, and not occurring in regular rows. Tabulae complete, few in 

 number. 



This species is apparently nearly related to Cladopora turgida, Rominger, 

 from which it can be readily distinguished by the comparative thinness 

 of its corallum and more delicate form of growth generally, and by the 

 smaller size of its calyces, which have thinner walls and are consequently 

 much closer together. 



Abundant in the Hamilton formation of Ontario, and found occasion- 

 ally in the Corniferous limestone of the same province. 



Cladopora frondosa, Nicholson. (Sp.) 



Alveolites frondosa, Nicholson. 1874. Geological Magazine, new series, vol. L, p. 15, 



pi. II., fig. 2 ; 1874, Palseon. of Ont., p. 57, fig. 16. 

 Cladopora Canadensis, Rominger. 1876. Geol. Sur. Mich., Foss. Corals, p. 48, pi. 



XIX., fig. 3. 

 Pachypora frondosa, Nicholson and Etheridge, jun., 1877. Jour. Linn. Soc, vol. XIII., 

 p. 362. 



Nicholson. 1879. Palseoz. Tab. Corals, p. 94, fig. 17. 

 n t, Whiteaves. 1889. Contr. to Can. Palseon., vol. I., pt. II., p. 121. 



Corallum irregularly palmate with a stout massive base, spreading 

 above into a thin lobate expansion ; three or four or probabl} 7 more inches 

 in height, somewhat less in breadth, from 1 to about 5 mm. thick in the 

 upper portion, and sometimes attaining a diameter of as much as 23 mm. 

 near the base. Corallites subpolygonal or circular, *3 mm. in average 

 diameter, beginning with moderately thin walls that become gradually 

 thickened as they [proceed outward from the central axial plane to the 

 surface on both sides, where their greatest thickness, which is often con- 

 siderable, especially in the basal portion of the corallum, is reached. Caly- 

 ces small, lunate or crescentic, about *6 or *7 mm. in breadth, provided 

 below with a sharp lip that is more or less prominent and often depressed 

 below the general level ; generally about their own breadth apart, or even 



