328 MISS DONALD ON PROTEROZOIC GASTEROPODA [May 1902, 
itself. There is a shallow groove immediately above the band, and 
several fine threads ornament the surface. A short distance beneath 
the band is a subangularity, below which the base appears rather 
flattened ; between this angularity and the band there is also a slight 
thread. Aperture imperfectly known. 
Remarks and Resemblances.—there is but one specimen 
of this species at present known, and it is in Mrs. Gray’s collection. 
It resembles somewhat C. obscura, Portl., but the whorls appear to 
be broader and the lines of growth more oblique than in that species, 
of which the only examples are so badly preserved that it is difficult 
to make a just comparison. 
Dimensions.—Length=36 millimetres; width=14 mm. 
Locality and Horizon.—Thraive Glen, in beds of Upper Bala 
age [Lapworth]. 
CyrrrostRopHa ORpovix, sp. nov. (Pl. VIII, figs. 5 & 5a.) 
Diagnosis.—Shell elongated, turreted, composed of more than 
nine whorls. Whorls increasing gradually, more or less convex, 
but slightly flattened above. Band submedian on the body-whorl, 
but below the middle of the earlier whorls, concave, and bounded 
on each side by a strong raised thread. Ornamentation consisting 
of a ridge or swelling just below the suture, and several fine spiral 
_lines, the strongest of which is a short distance above the band, 
bounding a space less than the width of the band. Lines of growth 
sloping back to the band above, with but slight obliquity, and 
advancing below with greater obliquity , not seen on the band itself. 
Aperture “imperfectly known, 
Remarks and Resemblances.—tThis species, so fan as | know, 
is at present represented by only three specimens in Mrs, Gray’s 
collection, and they are all more or less imperfect and crushed. 
The ornamentation is indistinct at the best, and is not seen on the 
earlier whorls. C. Ordoviv somewhat resembles Hormotoma 
Grayiana, but is distinguished from it by being more slender, by the 
spiral ornamentation, and by the lesser obliquity of the lines of 
growth. 
Dimensions.—The largest specimen is figured in Pl. VIII, 
figs. 5 & 5a, and consists of seven whorls, both apex and base 
being broken; it measures 25 millimetres in length, and the pen- 
ultimate whorl measures about 7°25 mm. in width. “Another example 
has eight and a half whorls in a length of 22 millimetres. 
Locality and Horizon,—Shalloch Mill (Ayrshire), in beds of 
Middle Bala age [ Lapworth]. 
Genus Hormotoma, Salt. 
Subgenus GoNnrosPiRA, nov. 
Diagnosis.—Shell elongated, composed of numerous gradually 
increasing whorls. Whorls angular near the middle, surface smooth. 
A narrow, prominent, more or less convex and indistinctly limited 
band on the angle. Lines of growth sloping back to the band 
