546 H. A. NICHOLSON ON THE GASTEROPODA OF 



of expansion. Judging from the figure given by Hall, the carina, 

 also, would appear to be very broad and flat, which is not the case in 

 M. Loganii. Better specimens would doubtless show that the two 

 species are separated by other characters. 



Formation and Locality. Guelph Limestone ; Elora, "Western 

 Ontario. It has also been quoted from the same formation in Ohio. 



Mttrchisonia bivittata, Hall. Plate XXYI. fig. 7. 



M. hivittata, Hall, Pal. ET. Y. vol. ii. p. 345, pi. lxxxiii. figs. 1 a, b. 



In the condition of preservation in which the specimens in the 

 Guelph dolomites occur, this species can only be recognized, with any 

 certainty, in examples which exhibit the interior of the shell. In 

 these we find the characteristic peculiarity that the columella is 

 marked with a conspicuous double spiral fold, the obliquity of which 

 varies in different specimens. So far as can be judged, such specimens, 

 all of which are fragmentary, appear to expand with moderate rapidity, 

 and to have an apical angle of about 15°, the number of whorls being 

 unknown, but stated by Hall as more than twelve. 



Specimens exhibiting the exterior, but not showing the columella, 

 cannot, in the present state of our knowledge, be certainly referred to 

 M. hivittata. One small example (fig. 8), which, from its general form 

 and proportions, I should be disposed to refer to this species, is about 

 twenty lines long, and consists of about six whorls. The apical angle 

 is about 18° ; and the whorls are carinated about their middle, being 

 convex below the carina and slightly concave above it. The body- 

 whorl is expanded towards the aperture. I cannot, however, affirm 

 with any certainty that this is really a young individual of M. hi- 

 vittata. 



Formation and Locality. Guelph Limestones ; Elora and Hespeler, 

 Western Ontario. 



Murchisonia (?) longtspiba, Hall. Plate XXYI. figs. 11, 12. 



M. longispira, Hall, Pal. N. Y. vol. ii. p. 345, pi. lxxxiii. figs. 2 a, h. 



Spire long, turreted, composed of numerous volutions. The whorls 

 increase very slowly in size in proceeding from the apex to the base. 

 Apical angle about 10° or less. Whorls rounded externally, with a 

 carina below the centre (Hall). Columella remarkably thick, rounded, 

 without being in any way twisted or folded. 



This species may be recognized by its slender elongated spire 

 and numerous volutions. None of my specimens are perfect, the 

 largest being a fragment ten lines long, two and a half lines wide at 

 the broken base, and rather more than one line in width at the broken 

 summit. The most conspicuous character of longitudinal sections is 

 the great thickness of the simply rounded columella, which occupies 

 nearly one half of the total thickness of the whorls. 



Professor Hall apparently regards this species as being a Loxonema ; 

 but I do not know upon what grounds he has changed his original 

 determination, and none of my specimens shows the surface. 



Formation and Locality. Guelph Limestones; Elora, Western 

 Ontario. 



