83 



external shape of its shell and its internal peculiarities. Figure 5 on 

 Plate 12, which represents a gutta-percha impression of a natural mould 

 of the exterior of the shell from Belwood, shows that it is rather slender 

 and composed of about twelve volutions. Those of the spire are com- 

 pressed convex above and distinctly angulated below the mid-height ; the 

 suture is deeply impressed : the outer volution is angulated, apparently 

 with a spiral band, about the mid-height, and rounded and apparently 

 narrowly umbilicated below. Figure 6, on the same plate, represents a 

 longitudinal section of the upper portion ^f the shell, also from Belwood. 

 It shows that the transverse shelly partitions of the earlier volutions of 

 the spire are concave, numerous, and placed at intervals of from one to 

 two millimetres apart. Other specimens from the same localities show 

 that the columella is hollow throughout, as previously stated on page 78. 



M. bivitlata seems to be most nearly related to M. Estella, Billings, 

 but in the latter species the shell is still more slender and composed of 

 more than fifteen volutions. The diagrammatic representations of M. 

 bivittata on page 339 of the " Geology of Canada " is very unsatisfactory 

 and does not give a correct idea of its characters. 



BBB. Volutions more than twelve. 

 MuECHisoNiA Estella, Billings. 



Murchisonia Estella, Billings. .1862. Geol. Surv. Canada, Pal. Foss., vol. I., p. 157, 



fig. 139. 



Gait, E. Billings, 1857, an imperfect mould of the outside of the shell, 

 consisting of fifteen volutions, and Dr. R. Bell, 1861, a similar specimen. 

 According to Mr. Billings "this species is allied to M. longispira, Hall," 

 " but is more acutely angular in the whorls." 



MUECHISONIA LONGISPIRA, Hall. 



Jlurchisonia longispira, Hall 1852. Pal. N. York, vol. II., p. 345, pi. 83, 



figs. 2, a-b. 

 " " Nicholson... 1875. Rep. Pal. Pro v. Ont., p. 70, pi. 3, figs. 



11 and 12. 



Gait, A. Murray, 1847, E. Billings, 1857, and Dr. R. Bell, 1861; 

 Elora, T. C. Weston, 1861, and D. Boyle, 1880; Hespeler, T. C. Weston, 

 1871 ; Guelph, Professor H. A. Nicholson ; Durham, J. Townsend, 

 1878-82. M. longispira is remarkable for its extremely elongated and 

 very slender spire, also for its numerous volutions, which are stated to be 

 " rounded on the surface, and carinated below the centre." Professor Hall 

 says that he has counted twenty-five volutions in a mould of this species 



