116 ROYAL SOCIETY OF CANADA 



The lip of the shell is somewhat campanulate on the ventral side. 



There is a considerable difference in form between the adult and the 

 youni^ of this sjiccies, for where the width is 3 mm., the dcjith (from 

 ventral to dorsal side) is 1^ mm. ; and where it is 5 mm. in width it is 3 

 to 3^ mm. in depth ; but at the oritice of an adult tube where the width 

 is 17 tnin., the depth is 13 mm. This rounding of the tube in the distal 

 half is accom))aniod by a transfer of a part of the dorsal surface to the 

 ventral side ; the transfer begins when the width of the shell is about 6 

 mm. and gradually increases until the adult condition is reached. Along 

 the line on the ventral side, where the course of the striœ is changed, a 

 low ridge is developed on the surface of the tube to which a shallow 

 furrow on each side is complementary. 



The shell is frequently decollated at the small end, the mutilation 

 occurring at the line of a septum. Or possibly the septum is in some 

 cases a secondary growth produced after the decollation occurred. This 

 seems possible, as the lowest septum is often found to project as a callus 

 beyond the outline of the outer surface of the tube, as though the animal 

 had power to repair and strengthen its tube at the proximal end. Several 

 of the decollated shells have a second septum dividing a small chamber 

 at the proximal end of the tube. The exposed septum at the lower end 

 becomes as thick as the side-walls of the tube. 



Sculpture. — The obscurity of the stria? spoken of by Billings applies 

 chiefly to the dorsal side, though even on this side, when the outer surface 

 is well shown, it is seen to be traversed b}' fine, closely set, arched strife. 

 On this side also there are faint undulations that are arched and conform 

 in a general way to the course of the striiv on this side. 



On the ventral side the stria^, though fine are quite distinct when 

 viewed with a lens. Many shells also exhibit undulations of the surface 

 more or less distinct ; on some shells they arc continuous from the small 

 end and are about twenty in number. They are not all of equal width as 

 in Orthoceras, but some are narrower than others as in Tubicolous 

 worms, etc., and they are proportionately closer toward the apex of the 

 shell. 



Hillings gives the rate of tapering in this species as four or five lines 

 to an inch. 1 have found the proportion 1 to 3 prevalent, though one of 

 1 to 34 was observed. Billings makes the apical angle 20° ; this id the 

 angle at the aperture, at the proximal end it is greater. 



Operculum. 



Billings makes no reference to the operculum of this species. But it 

 is not i-are in connection with the tube and has the following character : 

 The outline is broadly oval and the dorsal part, including the nucleus, is 

 bent upward from the dorsal at an angle of 25° ; the nucleus is raised 



