wmbe.] CANADIAN PALiEOZOIC CORALS. 105 



Petraia profunda, Conrad. (!Sp.) 



Plate VI., figs. 5, 5a, 5b. 



Cyathophyllum profundum, Conrad. 1843. Proc. Acad. Nat. Sci. Philadelphia, p. 335. 

 Streptelasma profunda, Hall. 1847. Palseon. New York, vol. I., p. 49, pi. 12, figs. 4, 

 4a— e. 



Corallum simple, turbinate, very slightly curved, sharply pointed below, 

 higher than broad and apparently seldom more than about 3 ceno. in length. 

 Outer surface marked by transverse growth annulations of unequal 

 strength at irregular distances apart, and by narrow, distinct, long- 

 itudinal septal furrows. Calyx wide and very deep reaching almost to 

 the base of the corallum. Septa, of two orders, primary and secondary, 

 alternating, denticulated at their edges, carinated on their sides and 

 numbering in all in well developed individuals as many as ninety. The 

 primaries extend to the bottom of the cup as thin lamellae standing out 

 about 2 mm. from the side walls, the secondaries reach only about half 

 way to the bottom and are little more than uniserial rows of denticles. 

 Both kinds of septa become low and obtusely rounded near the mouth of 

 the calyx. Three principal septa are developed, a cardinal septum and 

 two lateral or alar septa ; the bilateral symmetry of the septa and their 

 pinnate arrangement on the convexly curved or dorsal side of the coral- 

 lum is distinctly noticeable. 



A particularly well preserved specimen in the collection is 30 mm. 

 high and 26mm. broad at the top. 



Locality. — La Petite Chaudiere, Ottawa, Ont., collected by E. Billings, 

 also Paquette's Rapids, Ottawa River, collected by T. C. Weston in 1872. 

 Birdseye and Black River formation. 



Petraia aperta, Billings. 



Petraia aperta, Billings. 1862. Palaeoz. Foss., vol. I., p. 102, figs. 89a and b. 



Original description. — "Corallum simple, turbinate, short, widely 

 expanding ; cup deep, broadly concave in the bottom, with a distinct 

 septal fossette on one side. Radiating septa from one hundred to one 

 hundred and fifty. Surface with a few annulations of growth, and finely 

 marked with the longitudinal septal striae, of which there are from five 

 to seven in the width of one line. The specimens are from four to six 

 lines in height, and from eight to twelve lines in width at the margin. 

 Depth of the cup about half the height. The point of attachment is very 

 nearly central." 



