Bullia callosa
A marine snail with a distinctive chestnut callosity on the shell.
Bullia callosa, also called the callused bullia, is a marine gastropod mollusk in the Nassariidae family—the same group as Nassa mud snails and dog whelks. Its shell ranges from 18 mm to 50 mm in length, is elongated and cylindrical, and has a smooth, shiny exterior colored like coffee with milk. The pointed spire consists of six whorls that are not convex; each whorl is coated with a layer of material that turns chestnut at the base. This layer is thickest on the body whorl and extends, widening, to the left lip, where it forms a large, semicircular callosity that is deep chestnut with a white border. A fawn-colored line separates each whorl just below each suture. The ovate aperture is pale fawn, widens toward the middle, and is strongly notched at its base. The columella is curved, calloused, smooth, and fawn-colored; its callosity is oblique, thick, and furrowed, much shorter than the outer lip. From the lower part of the columella, a groove runs obliquely across the back of the shell, ending at the sharp front corner of the right lip. This species is found in marine waters from Angola to Mozambique.
Quick Facts
- Genus
- Bullia
- Species
- callosa
Facts from the source article.
Lore & Background
The shell of Bullia callosa is elongated and cylindrical, with a smooth, shining surface colored like coffee and milk. The elongated spire is pointed and composed of six whorls that are not convex. Each whorl is covered between the sutures with a layer of matter that becomes chestnut at the base; this layer is much thicker on the body whorl and continues to the left lip, forming a large semicircular callosity of deep chestnut bordered with white. The whorls are separated by a fawn-colored line just below each suture. The aperture is ovate, pale fawn, dilated toward the middle, and strongly emarginated at the base. The columella is arcuated, callous, fawn-colored, and smooth; its callosity is oblique, thick, furrowed, and much shorter than the outer lip. From the lower part of the columella, a stria stretches obliquely across the back of the shell to the anterior angle of the sharp right lip.
Reader's Guide
Bullia callosa is a representative of the Nassariidae family, a group of marine gastropods commonly known as Nassa mud snails or dog whelks. The species is distinguished by the prominent callosity on its left lip, a feature that gives it the common name 'callused bullia.' The shell's smooth, polished surface and coffee-and-milk coloration, combined with the deep chestnut callosity bordered in white, make it visually distinctive among its relatives. Its distribution along the coast from Angola to Mozambique places it within the warm waters of southeastern Africa. The detailed description of the shell's sutures, columella, and aperture reflects the careful morphological study typical of malacological work. While the species is not noted for any particular ecological or economic significance in the available information, its inclusion in identification guides for South African seashells underscores its role in regional biodiversity. The shell's size range—from 18 mm to 50 mm—indicates moderate variation among individuals. The callosity and stria on the back of the shell are key diagnostic traits for distinguishing Bullia callosa from other nassariids.
Did You Know?
- The shell length of Bullia callosa varies between 18 mm and 50 mm.
- The callosity on the left lip is semicircular, deep chestnut, and bordered with white.
- This marine species occurs from Angola to Mozambique.
More in Marine Snails: Ceriths, Nassas and Conchs, Part 2 1-24
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