J8 



GEOLOC.ICAL AND NATURAL HISTORY SURVEY OF CANADA. 



Batostoma Ottawaense. (N". Sp.) 

 Plate II:, figs. 1-]/. 





Batostoma Ottawaense. (N. Sp.; A silicified fragment of the ramose zoarium 

 of this species, from the Black Iliver Formation of Paquette's Rapids on the 

 Ottawa River. Natural size. 



Zoarium ramoso to frondesccnt. Tho ramose forms consist of stoul, 

 cylindrical or sub-cylindrical, dichotomous branches, varying in thickness 

 from 10 to 16 mm. The frondesccnt forms arc palmate with compressed 

 branches measuring from 10 to 18 mm. in breadth at their bases and 

 taporing towards their extremities to an obtuse point. Greatest breadth 

 of the frond 4 cent, ; thickness about 6 mm. Surface of both forms 

 covered with small and inconspicuous monticules placed at variable dis- 

 tances apart and occupied by from ten to fifteen cells slightly larger than 

 tho average. Cell-apertures very variable in outline, usually sub-circular, 

 especially on weathered surfaces. Thej^ avernge about '5 mm. in 

 di£%metcr. 



Tangential sections show that in the axial portion of tho zoarium the 

 larger tubes are angular, polygonal, thin-walled and very variable in size 

 and shape. As they approach the surface they become greatly thickened 

 by a secondary deposit of sclererchyma of fibious structure. Tho cells 



