MURCHISONIA. 
317 
4. MuRcmsoNiA LoxoNBMOiDES, n. sp. PI. XXX, figs. 17, 18, 18 a. 
1853. Plexjeotomabia biiineata, Sandherger (not (P Archiac and de VerneuiT). 
Verst. Ehein. Nassau, p. 204, pi. xxiv, 
fig. 17. 
Description. — Shell very elongate, large, acuminate, coiled in more than eight 
rather broad whorls. Apex probably acute. Spire regularly and slowly increasing. 
Suture rather shallow and obtuse. Whorls rather broad, moderately and regularly 
convex, the widest point being about three-quarters the way down from the suture. 
Sinus-band situated on the widest point, rather narrow, prominent, bounded by two 
large rounded ridges, of which the upper is the largest. Ornament consisting of two 
small spiral ridges below the sinus-band, and two or three slight indications of spiral 
lines above it ; the whole crossed by numerous, very fine, regular, almost micro- 
scopic, transverse lines, arching gently backwards on the upper part of the 
whorls, recurved on the suture, and running obliquely forward below it. Mouth 
unseen. Shell-structure thin. No umbilicus. 
Size. — Height 50 mm., width 22 mm. (specimen defective). 
Localities. — Three specimens from Wolborough, and one probably from 
Lummaton, are in the Torquay Museum. 
Remarks. — This species is characterised by its regular shape, rather broad and 
evenly convex whorls, and delicate non-tuberculate ornament. It presents so strong 
a general resemblance to Loxonema reticulatum, Phillips, that specimens which 
want the surface may easily be confounded, but of course when any of the ornament 
can be seen the shells are at once distinguishable. 
M. bilineata, Sandberger (not Goldfuss), very closely resembles this shell. Its 
whorls are somewhat narrower, and Sandberger mentions only a single spiral 
ridge below the sinus-band which is not shown in the figure, but the position 
of the sinus-band is identical, and on the whole it seems probable that it is 
the same species. 
Affinities. — The points above mentioned remove it so far from all the varieties 
of M. turhinata, Schlotheim, sp., that it evidently is specifically distinct. It 
approaches M. trepomena more nearly ; and the ornamentation is so similar that 
possibly it may prove to be no more than a variety of it ; but as that species, 
unlike M. turhinata, Schlotheim, seems to vary very little, there appears more 
reason for regarding it as distinct. The whorls in this shell are much broader 
and more convex, the sinus-band is decidedly lower on the whorls, and the 
ornamentation is coarser. 
Turritella Ponti, Groldfuss,^ approaches this shell closely in ornament, but the 
1 1844, Goldfuss, ' Petref. Germ.,' vol. iii, p. 104, pi. cxcvi, figs. 2 a,!). 
