Description. — Shell very fragile, conically elongated. Protoconch as most of the species of the genus with a little more than one whorl, a nucleus of about 20 µm and a diameter of about 200 µm, with numerous radial wrinkles. The first whorl of the teleoconch begins, as in other species, with an area that is practically smooth with only fine striae, and only ¼ of whorl later a depression begins which finally becomes a small shelf. Over the next whorls it will separate both parts of the whorl. The upper part has numerous very fine and close curved axial lines and occupies between 30 and 34% of the height of the whorl. In the lower part there are about 9 wide but attenuated and rather regular spiral cordlets, which are crossed by numerous axial growth lines, which, in the upper part are opisthocyrt while in the lower part are prosocyrt. After the 4th whorl the peripheral sulcus that separates the two areas of the whorl is more attenuated. Aperture oval, columella a little prosocline, reflected outwards and delimiting a narrow umbilical fissure.
Distribution. — Islas Galapagos and Ecuador, between latitude 0 and l°35’N. Live material was collected between 6 and 12 m.
Etymology. — The specific name refers to the archipelago where the species has been collected.
Remarks. — This species should be compared with those living in adjacent areas.
Murchisonella occidentalis is larger, with narrower (20-25% against 30-35% in M. galapagensis spec. nov.) subsutural part of the whorls which has less evident axial striae and has fine spiral lines; in the lower part the axial striation is finer. In M. galapagensis spec. nov. the teleoconch has 1/4 of a whorl before the depression commences, while in M. occidentalis there is between 1/2 and 3/4 of a whorl.