The other kind of land snail

kw: species summaries, natural history, natural science, museums, research, photographs

I spent more than two years, in my work at the Delaware Museum of Natural History, cleaning up/correcting and loading data for their collections of terrestrial gastropods, informally known as land snails. Correction: the past 2+ years I worked with the pulmonate terrestrial snails. They are called "pulmonate" because they have lungs, though really they are modified gills in an internal cavity where they can be kept moist, and muscular contractions pump air in and out, like real lungs.

That is not the only kind of land snail. The other great division is the operculate terrestrial snails. They are called "operculate" because they have an operculum, a kind of door that they can use to seal the shell shut, to keep water in, because they have gills inside the shell, and also to keep predators out. Many marine snail species also have an operculum, used to avoid desiccation when they get stranded above the tide line for a while, and even more to keep predators out.

The pulmonate lifestyle is apparently the easier, because there are many more species of pulmonates than operculates. In the DMNH collection, 95% of the land snail collection is pulmonates, more than 40,000 lots versus about 2,000 lots or operculate land snails.

Thus, my last project is to clean up, and load, all the data for the operculates. The first major family that I encountered is the Annulariidae. Many of these have a flared aperture, as shown in these two images:

This image is roughly life size (the museum label is 3" long). The species Chondropoma bairense Torre & Bartsch 1938 is a little prettier than most of its kin, and larger. Here, "Chondro-" relates to "grain", and many species in this genus are little larger than grains of corn. The flared aperture is characteristic of species in many genera of the Annulariidae.

This one is called "bairense" because it was first found at Baire, Cuba, which is in the south, in the state of Santiago de Cuba, west of Guantanamo. Hoyo de la Reyes can mean "king's pit" or "-hole", but here it probably refers to a steep valley.

From the differences between the older label and the one that C.L. Richardson typed up we can see why it is helpful to have all the labels possible with a specimen. Richardson simply left out the name of the town on his own label!

Here is a closeup of the shells. Sadly, both have their tips knocked off. This is the only lot of this species in the DMNH collection, so we must make do with what we have. I find it fascinating that there is ribbing along the outside of the whorls, but the shell on the right also reveals longitudinal ridges in the omphalos (a synonym of "navel" or belly-button; it refers to the central hole where the whorls come together. Not all snail species have one, including the next one shown).

I picked one other species to show, because of its bristly appearance and because one shell still has the operculum:

In spite of the way the name is spelled on both labels, this species is Blaesospira echinus (Wright, 1864). The parentheses indicate that the genus name has been changed, but I don't know the history. I don't know what the genus name means, but I suspect it means something like "open spiral" because the whorls of the shell are not in contact.

The species name is easier: "echinus" means "spiny", and this little critter is truly spiny. The mogote (isolated hill) named "El Queque" is a well known snail collecting locality in the Viñales area of the state of Pinar del Rio, Cuba. 

This image is about 40% larger than life size; the shells seldom exceed a centimeter in length or diameter. These spiky little critters are even more impressive when magnified:

Here you can see that one of the shells still has an operculum in its aperture. Opercula frequently have a spiral structure like this one. The wavy rim of the apertures hint at the way the spikes are formed. They are hollow with open tips. These lovely little shells are very popular with collectors, which makes me wonder if they are still to be found there. Few specimens from Cuba have found their way into American collections since the Castro regime began in 1959.

I should also mention that some taxonomists place this genus in the family Pomatiidae (once called Pomatiasidae). What with DNA sequencing and other tools of molecular biology, the taxonomy of mollusks in general is being reviewed and revised more than ever.