114 CONTRIBUTIONS TO CANADIAN PALAEONTOLOGY. 



nearly 4 cent, with a diameter above of about 2-2 cent, and an average 

 length rather over 2 cent. Outer surface conspicuously marked by longi- 

 tudinal septal furrows that indicate the pinnate mode of addition of new 

 septa and the positions of the cardinal and alar septa, transverse growth 

 markings faint. Calyx with thin erect sides, its depth often nearly equal 

 to about one-half the height of the corallum. Septa about fifty in number 

 in moderately large specimens, of two sizes, alternating, the primaries 

 passing to or nearly to the centre, the secondaries small and projecting 

 only slightly inward beyond the mural investment. The inner ends of 

 the primary septa often coalesce in sets of twos or threes near the centre 

 of the visceral chamber. In longitudinal sections, thin, delicate dissepi- 

 ments, partaking somewhat of the nature of tabulse, are seen to arch 

 upward and inward in the interseptal loculi to the centre, forming with 

 the inner ends of the primary septa an axial cellulose structure that has 

 a convex surface at the bottom of the cup. In the calyx the primary 

 septa standing out prominently from the wall are seen to be carinated on 

 their sides and to have denticulated free edges, the secondaries being 

 reduced almost to uniserial rows of denticles ; in longitudinal sections of 

 the corallum the inner edges of the primaries have the appearance of 

 being strongly serrated. 



Localities.— Grimshj, Ont., T. C. Weston, 1887 ; Thorold, Ont., Eev. 

 J. M. Goodwillie ; Isle of Mann (Burnt Island), Lake Temiscaming, Que., 

 A. E. Barlow, 1893. Niagara formation. 



Stkeptblasma latusculum, Billings. (Sp.) 

 Plate VI., figs. 9, 9a. 



Petraia latusoula, Billings, 1862. Palaeoz., Foss., vol. I., p. 104, fi}<s. 92(i and 6. 



Billings, 1866. Cat. Sil. Foss. of Anticosti, p. 33. 

 Streptelasma corniculum, Whiteaves. 1880. Rep. of Progress for 1878- -79, Geol. Survey 



of Canada, p. 49c. 

 Streptelasma rusticum, Whiteaves, 1895. Palseoz. Foss., vol. III., pt. II., p. 113. 



Corallum simple, conical, short, at first gaining in breadth rapidly, then 

 becoming more cylindrical above, slightly curved, pointed below, annu- 

 lated by growth accretions and longitudinally striated by moderately dis- 

 tinct septal furrows ; length of largest type specimen (fig. 92, original 

 description), measured along an imaginary axial line, 27 mm., maximum 

 breadth 22 mm., immature corallites generally broader than high. Calyx 

 with steep sides, its depth equal to about two-fifths of the height of the 

 corallum, in immature individuals rather deeper proportionately, its floor 

 convexly elevated and showing the primary septa as thin keels passing to 

 the centre. In the calyx the primary septa ascend as sharp-edged ridges, 



