RISSOA. 371 
An account of the R. cingilla has appeared in the ‘ British 
Mollusca.’ The R. pulcherrima, nonnull., is a dwarf, nearly 
ribless R. inconspicua, which is one of the most variable species 
in form, size and markings. In comparison, care must be 
taken not to examine what is called an adult R. pulcherrima 
with a young ‘inconspicua’ of the same size, but of larger 
growth, as it may lead to false ideas of distinctness: adult 
shells, of whatever growth, and in like manner, young shells, 
must be compared together, as the aperture in the two condi- 
tions is very different, there bemg in that of the young ones 
always a subangularity, but in those with completed peristomes 
it is nearly orbicular. 
I have lately received some minute shells collected in Zet- 
land; I have met with them occasionally on the South Devon 
coast. They are a partly dwarf or immature variety of 
that singularly variable species the Rissoa inconspicua, and 
are marked in the direction of the axis with about seven 
brownish-red lines that are tolerably regular and equidistant. 
I believe they are the long-lost species of Adams, “ lineis 
rubris notata. Apertura margine patentissima.” (Linn. 
Trans. vol. ii. p. 67.) With respect to the thickened or 
broad margin, it is rarely seen but in the completed shell, 
whether it be dwarf, or of a larger growth; and in the variety 
styled pulcherrima it is mostly wanting, probably in conse- 
quence of a depauperation from littoral causes, as the R. in- 
conspicua is usually a deep-water or coralline zone species. 
The so-called R. eximia is an undoubted Chemnitzia allied 
to C. excavata; I have described the shell, the animal being 
undiscovered, under the title of C. Barleet. 1 cannot speak 
of the R. anatina and R. ventrosa, not having met with them 
alive. 
The Turbo subumbilicatus of Montagu is still in obscurity ; 
it is perhaps a variety of one of the species of the estuaries, 
and if it could be identified, its position would probably be in 
this genus. I mention the Jeffreysia diaphana and J. opalina, 
because they have recently been styled Rissoe ; they appear 
from several characters to form the passage to the Chemnitzie. 
I think I have now named every Rissoa. 
2B2 
