Vol. 58.) REFERRED TO MURCA/ISONIA AND PLEUROTOMARLA. 3 
5 
Practical Geology, Jermyn Street, one of which is merely part of a 
section. The largest, which is the type (Pl. IX, fig. 4), consists of 
about thirteen whorls, and measures 22 millimetres in length, and 
7mm, in width. The Natural History Museum, South Kensington, 
and the Geological Survey Collection, Edinburgh Museum, each 
contain two small, badly-preserved examples. 
Locality and Horizon.—Durness Limestone, Sutherland, 
which is regarded as probably homotaxial with the Tremadoc 
Beds. 
LopHosPIRA BOREALIS, sp. nov. (Pl. IX, figs. 5 & 6.) 
Diagnosis.—Shell turreted, of medium height, composed of 
more than five angular whorls, which increase rather rapidly. 
There is a strong angle, near the middle of the whorls of the spire 
and somewhat above the middle of the body-whorl, which represents 
the sinus; a slighter angle below is situated at the suture. Outline 
nearly flat above the submedian angle, slightly concave between it 
and the lower one. Lines of growth very indistinct, apparently 
curving forward below the angle. Aperture subquadrate ; inner 
lip thickened. Umbilicus open. 
Remarks.—there is but one undoubted specimen of this species 
in the Geological Survey Collection, Edinburgh Museum; and it is 
merely an internal mould, consisting of four distinct whorls and a 
much worn apex, the actual number of whorls in which cannot be 
made out. On the upper part of the body-whorl are traces of a fine 
line just below the suture. The submedian keel is much weathered, 
but was probably trilineate. A shell (Pl. IX, fig. 6), of which only 
two whorls are preserved, may perhaps belong to this species; it 
differs in there being two finer keels below instead of a single strong 
one, and it also gives the impression of being more depressed. 
Resemblances.—tThis species differs from Z. bicincta (Hall)' in 
not possessing so strong a keel on the upper part of the whorl 
below the suture, and in the lines of growth being more oblique; 
the former characteristic also distinguishes it from ZL. obliqua, 
Ulrich ? (Murchisonya bicincta, Salt.). I have compared it with 
specimens of the latter species and the variety perangulata from 
Allumette Island in the Natural History Museum, South Kensington ; 
and find that it differs from all also in the sinual angle being more 
nearly central, and thus the upper flattened part of the whorl is 
almost equal to the lower concave part, and the whorls are wider. 
It is most like L. centralis, Ulrich,’ but it is likewise distinguished 
from it by the nearly central position of the sinual angle, and the 
lower keel being apparently stronger. It belongs probably to the 
Perangulata subsection of the Perangulata section of Ulrich.* 
Dimensions.—Length=about 19 millimetres; width=12 mm. 
Locality and Horizon.—Durness Limestone, Sutherland. 
* «Pal. N. Y- vol. i (1847) p. 177 & pl. xxxviii, figs. 5 a—h. 
* Final Rep. Geol. & Nat. Hist. Surv. Minnesota, vol. iii, pt. ii (1897) p. 965 
& pl. lxxii, figs, 6-8. 
3 bid. p. 979 & pl. lxxiii, fig. 9, ‘ Ibid. p. 962. 
