Description. — Shell relatively large, smooth, very fragile, without shoulder, with up to 11 or 12 slightly convex whorls; the suture is well marked. Protoconch approximately one whorl with a diameter of about 150 µm and a nucleus of about 40 µm. The first whorl of the teleoconch shows isolated spiral narrow furrows, which continue in small quantity on both parts of the following whorls. The whorls of the teleoconch are smooth with a slight and regular convexity; there is no obvious separation between the two parts of the whorl. The subsutural area has a sculpture formed by opisthocyrt growth lines that are strongly convex, while in the lower part of the whorls these growth lines are prosocyrt. These growth lines and isolated spiral furrows are the only noticeable sculpture. Aperture oval. Columella almost straight, slightly reflected and bordering a fissure shaped umbilicus. Dimensions: the largest shells from the Philippines reach up to 3.6 mm in height. A shell from Vanuatu is 4.5 mm high.
Distribution. — Philippines, New Caledonia and Vanuatu.
Etymology. — The specific name alludes to the scarcity of differentiating characteristics.
Remarks. — Some shells are more elongate and the number of whorls is slightly larger. As the other characteristics are the same we interpret this as intraspecific variation.
Murchisonella modesta spec. nov. may be differentiated from most of the species described above because it lacks any step, cordlet, cord or any other sculpture on the line of separation between the two parts of the whorls. The separation between both parts is only based on difference in microsculpture.