MURCHISONIA. 
309 
1888. MuiiCHisoNiA SPiNOSA, JEtlieridge. Ibid., vol. i, Pal., p. 164. 
1883. — — Prestwich. Geology, vol. ii, p. 79, pi. v, fig. 10. 
1889. PiiEUJiOTOMAEiA LATEViTTATA, KoJcen, JSTeues Jahrb. f. Min., Beil.-Band vi, 
p. 324, pL X, fig. 12. 
1889. MuECHisoNiA alF. eigeanulosa, Kohen. Ibid., Beil.-Band vi, p. 367, pi. 
xiv, fig. 5. 
Description. — Shell large, very variable, elevated, many-whorled, turrited, and 
frequently more or less coarsely tuberculated. Apex apparently rather sharp. 
Spire conical, more or less elongated, generally, but not always, far exceeding the 
body-whorl in height, coiled irregularly in about seven to ten volutions. Suture 
deep, acute, simple or frequently complicated by the ornament. Whorls swollen, 
angulated, variable in shape, generally bearing just below the suture a tuberculated 
ridge or row of tubercles, which are sometimes very large and nodulous, and about 
twelve to fourteen to the whorl, and having more rarely on the lower bend of the 
whorl another indistinct ridge or row of elongate tubercles. Sinus-band in the 
centre of the back, narrow, prominent, concave, bounded by two strong, sharp, lofty 
ridges. Growth-lines irregular, indistinct, moderately oblique, arching in a slightly 
sigmoidal curve back from the suture to the sinus-band, where they are recurved, 
and then sloping similarly forward on the lower part of the whorl. Mouth 
small, oblique, sub-ovate, bluntly and indistinctly pointed both above and below. 
Outer lip convex, deeply notched at the extremity of the sinus-band. Columella 
thickened, arched, rounded. Umbilicus absent, or occasionally present but very 
small. Shell-structure thin on the back of the whorls, thicker elsewhere. 
Size. — A very large specimen, wanting the body-whorls, measures 70 mm. high 
by 27 mm. wide. Other specimens, with the body-whorls, measure respectively 
70 mm. by 31 mm. ; 57 mm. by 30 mm. ; and 33 mm. by 22 mm. 
Localities. — This species is very common at Chudleigh, and is well represented 
from that locality in most collections. From Wolborough there are two specimens 
in Mr. Yicary's collection, three in the Torquay Museum, one in the British 
Museum, and one in my Collection. In the Torquay Museum are three small 
specimens which may have come from Lummaton. 
Remarks. — This shell is so variable that it is very difficult to give an exact 
description of it. If two of the extreme varieties were placed together without 
their connecting links, they would certainly be regarded as belonging to distinct 
species if not to distinct genera. Nevertheless, when a large number are examined 
together, it is at once seen that hardly two specimens are exactly alike, and that 
extreme varieties can be united in series of almost imperceptible Hnks, so that it 
is impossible to find a dividing line between them. Moreover, sometimes the 
shape, ornament, and coiling change their character in different parts of the same 
shell. This is strikingly seen in one of Mr. Vicary's specimens (PI. XXX, fig. 12), 
