Description. — The shell rather similar to those of the previous species. Protoconch with a diameter of about 180 µm, relatively wide 1 1/12 whorls) and a very small beginning (nucleus about 30 µm). Teleoconch: first whorl without axial lines showing spiral cordlets from the suture down; this first whorl ends without separation between the two parts of the whorl. In the second whorl the upper part of the subsutural area is granular without lines whilst on the lower part marked furrows appear. In the following whorls there is a clear separation between the two parts but without any elevation; on the upper part there are no growth lines but a more or less regular rough or granular surface, covering about 35-40% of the surface. On the lower part the furrows are wider and more visible, being 7-8 in number, and the growth lines are scarcely visible and prosocyrt. There is an umbilical fissure. Dimensions: 1.6 mm high.
Distribution. — Middle and eastern Mediterranean.
Etymology. — The specific name refers to the sea where the species has been collected.
Remarks. — This species has been recorded (Zenetos et al., 2003) from the Mediterranean as Murchisonella columna, assumed to be a species introduced from the Red Sea. In reality M. mediterranea spec. nov. is unrelated to that species. The protoconch was perfectly illustrated by Bogi et al. (1995: figs 2M, 3M) showing a very small nucleus and larger spire in comparison to other known species. It has little or no similarity to other East Atlantic species:
The protoconch of M. africana spec. nov. has a smaller diameter, the upper part of the whorls is not rough but has furrows; the separation of both parts of the whorls is more evident in M. mediterranea spec, nov.; the lower part has less distinct furrows and more marked growth lines.
Murchisonella saotomensis spec. nov. has a slightly smaller protoconch, the upper part of the whorls is slightly narrower and appears before the end of the first whorl, with a more oblique sculpture; in the lower part there are cordlets instead of furrows.
Murchisonella angolensis spec. nov. has a protoconch with a larger diameter (200 µm), the teleoconch whorls have a more quickly increasing diameter, the subsutural zone is very narrow (only 15-20% of the height), the upper part of the whorl is not rough, whereas the lower part has a larger number of furrows in the same space.
Murchisonella arabica Bandel, 2005, found in the Red Sea, has a clear shoulder with a spiral cord separating the two parts of the whorl; the sculpture is different with scarcely appreciable spiral cordlets formed by narrow furrows and predominant axial cordlets formed by numerous ribs; the protoconch has a similar diameter but with almost half a whorl more and a larger nucleus.