334 MISS DONALD ON PROTEROZOIC GASTEROPODA | May 1902, 
LopHosPirs VARIABILIS, sp. nov. (Pl. IX, figs. 7-10.) 
Murchisonia gyrogonia, pars, J. Horne & B. N. Peach, 1899, Mem. Geol. Surv. 
‘Silur. Rocks of Britain’ vol. i, p.682; (?) J. Horne, B. N. Peach, & A. Macconochie, 
1901, in‘ Fauna, Flora, & Geol. of Clyde Area’ publ. by Local Com. for Meeting of 
Brit. Assoc. Glasgow, pp. 428 & 438; non F. M‘Coy, 1855, ‘ Brit. Palzoz. Foss.’ p. 298 
& pl. 1, fig. 43. 
Diagnosis.—Shell turreted, composed of about nine whorls. 
Whorls increasing somewhat rapidly, the two apical ones apparently 
convex, the rest possessing a strong angle below the middle, where 
the band is situated; body-whorl convexo-concave above, the 
earlier whorls not so convex above, but having a raised thread 
immediately below the suture, slightly concave below the band. 
Base very convex, with a subangularity a short distance below the 
band, which is represented by a strong raised thread on the earlier 
whorls, appearing just above, or else hidden by, the suture. Band 
prominent, composed of three keels, the central one becoming very 
strong and convex on the body-whorl. Sinus deep and wide, the 
end pointed and almost triangular. Lines of growth sharp, nume- 
rous, fine lines being intercalated between stronger ones, retreating 
slightly above the band, almost vertical below. Ornamentation 
consisting of very fine and faint spiral lines. Aperture sub- 
quadrangular ; inner lip reflected. Umbilicus apparently closed. 
Remarks and Resemblances.—-There are eight specimens 
of this species in Mrs. Gray’s collection, and also two casts which 
probably belong to it. One of these has the outer lip well preserved, 
showing the sinus, which has the end and the greater portion of 
the sides intact. The sinus is remarkably broad, especially when 
compared with the width of the band on the earlier whorls, where 
it is much narrower than on the body-whorl. An example in the 
Geological Survey Collection, Edinburgh Museum, has part of the 
sinus intact, and it is similar in form, but not so well preserved. The 
specimens vary considerably in the height of the body-whorl: in some 
cases this may be partly the result of the manner of preservation, 
some being slightly compressed downward, while others are pressed 
upward. Members of the genus Lophospira are frequently charac- 
terized by irregularity in the coiling of the spire. This appears to 
be the species wholly, or in part, referred to as Murchisonia gyro- 
gonia, M‘Coy,} in the list of species published in the Scottish Survey 
Memoir, ‘Silur. Rocks of Britain’ vol. i (1899) p. 682. The speci- 
men just mentioned from Balclatchie is thus named in the Museum. 
It differs, however, from M. gyrogonia in the whorls being less flat 
above and below the band, in the band not being flange-like; also 
the angle on the body-whorl is not so pronounced in the adult. 
L. variabilis resembles Pleurotomaria Sybillina, Billings,” from the 
Island of Anticosti, but is distinguished by its greater height and 
more numerous whorls. It is also somewhat like LZ. tenuistriata, 
Ulrich,? from the Utica Group, but differs in the greater convexity 
1 ‘Brit. Paleoz. Foss.’ 1855, p. 293 & pl. 1 x, fig. 43. 
* Geol. Surv. Canada ‘Catal. Sil. Foss. Anticosti’ 1866, p. 54 & fig. 19. 
° Final Rep. Geol. & Nat. Hist. Surv. Minnesota, vol. iii, pt. ii (1897) 
p. 983 & pl. lxxii, figs. 48-50. 
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