Morum morrisoni

Morum morrisoni n. sp. can only be confused
with M. grande, the conchologically closest
congener, on account of its large adult size, and the structure of the columellar shield. On average,
shells of M. morrisoni n. sp. are larger, appear
less solid, and are of a paler yellow-and-white
colouration. The body whorl is less ventricose but
narrowly tapering anteriorly, the spire is slightly
taller, giving the shell a more triangular, elongate
general appearance, with straighter whorls, and a
squarish shoulder. The spire whorls are straighter
and less ventricose than in M. grande. That
species tends to have a more developed
columellar shield, showing stronger, more
elaborate pustules than M. morrisoni n. sp.
The most important difference is the composition
of the dorsal sculpture. In M. grande, there are
transverse ridges with a rounded profile. The
interstices between these ridges are narrow or as
wide as the ridges. The longitudinal varices are
rather indistinct. Between these varices there are
fine lamellae forming scaly processes whose outer
margins are somewhat curved back. In
M. morrisoni n. sp., the transverse ridges are
narrower than the interstices between them. The
varices are more prominent and more pointed,
with their tips bent towards the posterior. The
lamellae between them are much less developed
and finer, and their scaly processes are much less
developed or absent.
The only other congener of similar appearance is
Morum uchiyamai KURODA & HABE, 1961,
which differs by its slenderer shape, a more
pointed spire and by the columellar shield, which
is more calloused and much less pustulose. The
labral callus of M. uchiyamai is thicker and bent
up, showing numerous dark specks and larger
dark blotches. – Taken from the original description paper