>I have an interesting shell about which to inquire -
>Balcis martini A. Adams, 1854 (not sure if the author's
>name should bein parentheses).

Melanella was, ironically, the genus most often used in the 1800s.
Adams almost certainly described it as such. It was named after
Martini, so the specific name is martinii (with a double i).
>
>First of all, one of my books says these are parasitic; my
>question is parasitic on what animal?
>
>The other thing is that I am supposed to be pricing these
>for our club's shell sell at a local festival, and I do
>not have Rice's prices at hand.  The two specimens are 36
>mm. and about 30 mm., and they are gem; but the data is
>minimal.
>
>I did find the species on a past auction with a starting
>price of 2 euros.

>Eulimids are parasitic on echinoderms - sea cucumbers, sea urchins, and sea
>stars. I don't know what species B. martini feeds on. It's a very common
>species. $1.50 to $2.00 (each) would be a reasonable value.

Prices go up to $6.00US for a really big one (over 40mm). And these
are massive shells for the family.

>I found a couple of references which state that the genus Balcis is
>parasitic on holothurians, that is to say sea cucumbers.

Melanella is a holothurian ectoparasite; it burrows in the sand, but
when hungry it attaches itself for a suckle. It has a
fully-functional operculum.

I am not sure whether Balcis is an outright synonym of Melanella, but
most spp once included in Balcis belong in Melanella; this includes
the species in question. Anders Warén (Stockholm) is the expert on
Melanellidae. Here is his reply to my inquiry as to ID of a specimen
(I sent him an image of the 45mm beast):
>Seems to be Melanella major. Do not worry about synonymy; it is not
>settled at all.
>
>Anders

I have seen this species illustrated in books and offered by dealers
as B. martinii, B. grandis, B. candida (and no doubt there are other
names). This may be due to synonymy and/or confusion as to the
correct identity of these spp.

The upshot is that martinii, candida etc are doubtful names.