a new rib from tlie side of the suture ; the last whorl in an adult specimen 
has thirteen ribs and a double keel, the lower one of which is the most 
pronounced. Between the keels is a moderately broad baud of the sinus, 
which is itself covered with fxue ribs barely visible to the naked eye. The 
upper surface of the base is depressed and furnislied with eight or nine 
indistinct rihs, parallel with the band, and crossed by lines of growth, but 
not "ranular. The umbilicus is of moderate size, funnel-shaped, and smooth. 
The aperture is transverse and angular. 
Dimensions. — This species can reach twelve or fifteen millimetres in 
diameter, and a length of eight or ten millimetres. 
Delations and Differences. — It is related to P. radula^ de Ivoninck, 
by the number and regularity of its ribs, and by the granulations covering 
them. 
Horizon and Localities. — It is found in the Upper Carboniferous 
Limestone of Bolland, Yorkshire, and of Vise, Belgium. A single specimen 
was found in a greyish limestone, in a railway cutting between Maitland and 
Stony Creek. 
Pleueotomaeia humilis, Ij. G. de Komncli} 
PI. xxin, Pig. 14. 
This shell is of medium size, sigaretiform, and composed of three or 
four convex, spiral wdiorls slightly clasping, the last of which rapidly takes a 
considerable development. The surface is ornamented with numerous fine, 
lorngitudinal ribs, crossed perpendicularly by equally fine lines of growth. 
The band of the sinus is separated from the rest of the surface by two 
furrows, rather deeper than those separating the ribs. This species has no 
umbilicus ; its columella is very oblique ; its aperture is large and transversely 
oval ; its exterior margin is thin, and slightly sinuous in the middle. 
Dimensions. — The length is about fifteen millimetres, and the transverse 
diameter of the last whorl twenty millimetres. 
Delations and Differences . — This species is very like my P. Frenoyana^ 
but it differs in the proportions of its length and breadth, and also by its band 
which is not grooved, and by the transverse form of its aperture. 
1 [Mourlo7iia humilis, E. Etheridge, Junr., Procs. Lina. Soc. N. S. Wales, 1889, IV (2), p. 205; S. Austr. 
Pari. Papers, 1897, No. 127, p. 15, t. 1, f. 11 (?).— W.S.D.] 
