CAMBaO-SILURIAN MICRO-rAL/EONTOLOGY. 19 



in this region consoquontly lose thoir angularity, and bocomo rounded or 

 scmi-oval, somotimos narrow and bean-shaped. In some places the walls 

 throw out slender prolongations or blunt spines, those are the incomplete 

 diaphragms to bo described further on. (See plate IL, fig. lb.) The inter- 

 stilial tubes fill up the spaces between the larger ones and are best seen 

 in sections, ground a little below the surface of the zoarium where they 

 have not become obliterated, as in the peripheral region, by the secondary 

 deposit of sclerenchyma. In the axial region they are not met with at 

 all, as they do not extend far below the surface. Large spiniform tubuli 

 occur at the angles of junction between the larger tubes or in the sub- 

 stance of their walls; the sections of these tubuli are strongly defined by 

 a dark ring with a white spot in the centre, making them very conspicu- 

 ous objects in a tangential section. Excepting in places where the tubes 

 have been cut a little deeper, their original walls are barely distinguish- 

 able in the dense secondary deposit of sclerenchyma; but they maybe 

 detected hero and there as somewhat obscure lines connecting the spini- 

 form tubuli together. 



Longitudinal sections exhibit numerous diaphragms, some of which are 

 complete, but the greater number do not extend more than half way across 

 the tubes ; in some places they appear merely as obtuse spinous projec- 

 tions of the walls of the tubes. The diaphragms are generally straight, 

 sometimes slightly curved, and often rather oblique to the axis of the 

 tubes. Many of the incomplete diaphragms are thickened at their distal 

 extremity into a little knob. Like the walls of the tubes, the diaphragms 

 in the axial region of the zoarium are very slender an 1 only become 

 thickened as they approach the periphery. They are about half a tube 

 diameter apart. 



This species may be readily separated from its nearest ally — Batosioma 

 Jamesi, Nicholson, Sp. (the type of the genus) — by its numerous transverse 

 diaphragms and their peculiar incomplete development in many of the 

 colls. 



LocaHty and Formation. — This species is not uncommon in the upper 

 beJs of the Trenton Formation in the vicinity of the City of Ottawa. It 

 has also been found at Paquette's Eapids (Ottawa River) in the Black 

 River Formation. 



Collectors.—y^aMQv R. Billings, Ottawa City; J. RicharJson, Paquotte's 

 Rapids. 



