16 GEOLOGICAL AND NATURAL HISTORY SURVEY OF CANADA. 



Amplexopora SUPERBA. (N. Sp.) 



Plate IV., figs. Mc. 



Zoarium irregularly ramoso, very robust in its habit of growth ; branches 

 cylindrical, measuring from 10 to 12 mm. in their greatest diameter, the 

 longest measured gives about 20 centimetres as its greatest length. Sur- 

 face of the branches studded with slightly raised monticules, which 

 consist of cells rather larger than the average. Cell-apertures sub-poly- 

 gonal in outline, about three occupying the space of one mm., except 

 upon the monticules, where two or two and a-half suffice to fill the same 

 space. 



In tangential sections the colls appear to be somewhat rounded at their 

 angles, the original walls, which are quite distinct, being considerably 

 thickened near the surface of the zoarium by a secondary deposit of 

 sclerenchyma. Largo and conspicuous spiniform tubuli are distributed 

 at the angles of junction of the cell walls, and occasionally one is situated 

 on the lino between two of these angles, and when this occurs a slight 

 inward protrusion of tho cell wall is the result. 



Longitudinal sections show tho tubes to be thin-walled in the axial 

 region of tho zoarium, and to bo somewhat sparingly supplied with 

 straight, horizontal diaphragms; these become much more numerous, and 

 sometimes coalescent, near tho periphery, whore also tho walls of tho tubes 

 are much thickened. The tubos bend gradually upwards and outwards as 

 they approach tho surface. 



Tho present species may bo distinguished from Amplexopora rohusia, 

 Ulrich, to which it is closely allied, by tho possession of monticules, by 

 ilfl more conspicuous spiniform tubuli, as seen in tangential sections, and 

 by tho absence of the funnel-shaped diaphragms occurring in that 

 species. 



Locality and Formation.— 'This beautiful species appears to be rare. 

 Montreal, Que., Tronton Formation. 



Coliccto?\-^S\v ^Y. E. Logan. 



