129 
the lower bounding keel forming the greatest periphery of the 
shell. Sculpture of equal, equidistant, primary spiral ridges, with 
intermediate finer secondary ones, and the valleys concave, the 
whole crossed by slightly oblique lines, dividing the surface into 
a decussation of unequal rhomboidal spaces. 
Obs. — Phanerotrema is a genus established by Dr. Paul Fischer 
to receive Pleurotomaria labrosa, Hall,* * * § and other Pleurotomaroid 
shells resembling it, such as Pleurotomaria balteata , Phi'll, f It 
would appear to be a very necessary and good subdivision of the 
larger and more comprehensive genus Pleurotomaria , and will 
include those species with a rhomboidally ovate form, and more or 
less carinate body whorl, arising from the prominence of the band. 
Like P. labrosa , Hall, sp., our species attained a considerable 
size, as evinced by the well marked, but imperfectly preserved 
shell represented in PI. xix., fig. 4. It appears to be a more 
obliquely elongated shell than P. labrosa , with a narrower band, 
although larger in size, and a finer ornament. The American 
species is from the Upper Pentamerus Limestone of New York 
State, an horizon equivalent to that of the British Ludlow rocks. 
As regards the British species, P. australis , is decidedly a more 
depressed shell with smaller upper whorls. The former is from 
the Wenlock Limestone. 
Genus Murchisonia, d’Archiae and Be Verneuil , 1841. 
(Bull. Soc. Geol. France, XII., p. 154.) 
Murchisonia, sp . hid. 
Obs . — Ill-preserved examples, either too imperfect, or too much 
defaced with matrix, to be determinable, are in the Collection. 
The species has some points of resemblance with Murchisonia 
cingulata , Hisinger,! but the angularity of the whorls and position 
of the band do not coincide with those features of that species. 
The same may be said of another allied shell M. sinuosa , Sby., 
sp.§ Our species appears to me, on the other hand, to be allied 
to Murchisonia attenuata , His.,|| in which the band is nearly 
median in position ; the only point of difference I am able to 
indicate being the somewhat more angular whorls on the Gotland 
shell. Otherwise the latter and our Murchisonia appear to be 
closely allied. 
* Pal. N. York, 1859, III., p. 339, Atlas t. 66, f. 1-5. 
f Mem. Geol. Survey Gt. Brit., 1848, II., Pt. i., p. 358, t. 15, f. 1 — 2. 
J See Murchison’s Geol. Bussia, 1845, Pt. iii., t. 22, f. 7a and b; Lind' 
strom’s Sil. Gastropoda and Pteropoda of Gotland, 1884, t. 12, f. 9. 
§ Salter, Mem. Geol. Survey Gt. Brit., 1848, II., Pt. i., p.357, 1. 14, f. 2. 
|| Lindstrdm, loc . cit ., t. 12, f. 20 and 21. 
