112 ROYAL SOCIETY OF CANADA 



Size. — No complete example is known. Tlie mouth of the tube has 

 a width of G nun. The length, estimated from llie parts known, would 

 be about 40 mm. if not decollated. 



Tliis lube is frequently found ensheathed in that of other species. 



This species is near J/yolithes communis., Billings, in general iorm, 

 but the aperture dilfers ; in Billings's species there is a projecting dorsal 

 " lip," while in this the aperture is directly transverse on the dorsal side • 

 thei-e is also a ditierence in the sculpture, as there are no longitudinal 

 stria' on 0. pufjio. I have not found any of the thick shells rigured by 

 Walcott (Bull. No. 30, pi. xiv., tigs. 3/ and 'àg.) as belonging to H. communis. 



On the other hand the operculum figured by this author (fig. 3c) is 

 plainly that of an Orthotheca ; jjossibly there are two species confused 

 under Billings's name, of which Sd and e may represent an Orthotheca. 



Dr. Gerhard Holm has described from the Lower Cambrian of 

 Sweden two species which are near this one, and which he suj)poses when 

 better known may prove to be one and the same species, 0. DeGeeri and 

 0. Johnstrupi. The former is said to be perfectly flat along the middle 

 of the dorsal, and to be probably smooth ; in both these respects it ditlers 

 from 0. pu'jio. The latter (0. Johnstrupi) seems a more slender elongated 

 shell, and the sculpture differs.' 



Operculum (PI. VI., fig. 4e). 



(Of this species or the next.) Nearly flat. Elliptical in outline, 

 somewhat straightened on one side (doi-sal). Nucleus nearly central, 

 pointed ; from it a ridge extends on each side to the middle of the dorsal 

 and ventral margins ; these ridges widen as they go outward ; on the 

 ventral side there is a lower ridge on each side of the central one. A 

 shallow furrow, interrupted by the nucleus extends across the operculum 

 on the long diameter. 



Sculpture. — This consists of minute granulations, and of faint, fine 

 engirdling striit, with several heavier growth lines. 



Size. — Length, 5 mm ; width, 4 mm. 



The substance of this operculum appears to be thin, and some 

 examples show but little straightening on the dorsal side. 



Orthotheca sica (PI. VL, figs. 5^ to d). 



Orthothrcd sirii. Nut. Hi.st. Soc. N.B., Hvill. xviii., p. 193, pi. ii., figs. 5a to e and figs. 

 ()« and h. 



Elongated conical shell, sub-triangular in section, the back of the 

 ventral side being broadly rounded and the lateral angles more sharply 



' Swedish Cambrian Silurian Ilyulithidii-, &c., pp. 54, 50, pi. i., flg.s. 25 to 27 and 

 28 to 30. 



