318 
DEVONIAN FAUNA. 
transverse stride on the upper part of the whorls are coarser, the four carinse on 
the lower part are larger and more separated, and the whorls are almost as broad 
as high. Goldfuss does not recognise any sinus-band, but the similarity in other 
respects is so great that I am much under the impression that it existed, and that 
it is at least a kindred species to the present form. 
Pleurotomaria insignis, Bichwald,^ also seems rather similar, but the transverse 
stria3 are still more deeply* deflected, and the sinus-band is not so low down and is 
very indistinct. 
PI. nitida, Eichwald,^ has a flat sinus-band, and narrower and much more 
numerous whorls. 
5. MuECHisoNiA MARGAEiTA, n. sp. PI. XXX, figs. 19, 20, 20 a. 
Description. — Shell small, extremely elongate, turrited, of nine to fifteen 
whorls. Apex very sharp, sometimes produced, and twisted asymmetrically 
for the last three or four whorls. Spire very elongate and subulate, with narrow, 
triangular, slowly increasing whorls. Suture deep, linear, facing upwards. 
Whorls much exposed, bluntly triangular in section, with a strong, microscopically 
tuber culated hem or rounded rim immediately below the suture, followed by 
an indistinct groove, from which the line of contour spreads in a concave curve to 
the central and widest part of the whorl, which is sharply rounded, and then sinks 
in a similar curve to the lowest part, which bears a similar indistinct hem. Sinus- 
band central, rather broad, defined by minute raised threads outside linear grooves, 
within which is a row of close round tubercles forming the raised centre of the 
band. Ornamentation consisting of six or seven very minute spiral threads both 
above and below the sinus-band, and similar transverse threads sloping back- 
wards to, and forwards from, the sinus-band. Mouth short, oblique, and wide. 
Outer lip deeply and widely notched ; inner lip long. No umbilicus. 
Size. — Length of a specimen of about fifteen whorls, 21 mm. ; width, 5 mm. 
Locality. — Ohudleigh. Two specimens are in the Woodwardian Museum. 
Remarks. — The larger of these two specimens has rather narrower whorls than 
the other, and is a much more subulate shell, with fifteen whorls remaining. Some 
of the whorls of the nucleus are strangely twisted and elongated, and, though this 
might be accounted for by a crushing of the fossil, it has more the appearance of 
being a natural though, of course, accidental feature of the shell. The other 
specimen has only nine or ten whorls including the body-whorl. However, they 
^ 1860, Eicbwald, ' Letbsea Eossica,' p. 1165, pi. xliii, fig. 1. 
2 Ibid., p. 1179, pi. xliii, fig. 2. 
