Species Account

Allogramma formosa (Jeffreys, 1882)

Pandoroidea : Lyonsiidae

Tebble name: n/a
Smith & Heppell name: Lyonsia formosa Jeffreys, 1881

To size: To 15mm. Shell Structure: Thin, fragile. Equivalve: Equivalve. Equilateral: Inequilateral, beaks slightly in front of midline. Tumidity: Moderate. Outline: Subrectangular; anterior rounded, posterior truncate, ventral margin gently curved, dorsal margins long sloping gently. Contour: Umbos prominent; posterior area set off by a radial carina running from the beaks to the posterior ventral junction.

Sculpture: Anterior area with few oblique weak ridges, anterior and median areas with dense, radial rows of minute spines, these larger on dorsal anterior area; posterior area with radial riblets bearing spines, these becoming larger on dorsal area and projecting above the margin. Margin: Inner margin smooth. Ligament: Small, set on a shallow internal lithodesma below the beaks. Hinge: Lacking teeth. Pallial Musculature: Obscure. Periostracum: Obscure. Colour: White.

Distribution & Ecology

Mostly from lower slope and abyssal depths, widely distributed in the North Atlantic including Rockall Trough and Porcupine Bight.

Depth Range
Bathyal (500 - 2000m)
Abyssal Rise (2000 - 4000m)

Additional Information & Related Species

Juvenile Description

Small shells are more trapezoidal in outline, the anterior distinctly narrower than posterior.

Related Species

Pandoroidea : Lyonsiidae


Listed are literature citing Allogramma formosa (Jeffreys, 1882). Reference containing the species Type Description is highlighted.

Jeffreys J.G. 1882. On the Mollusca procured during the ‘Lightning’ and ‘Porcupine’ Expeditions, 1868-70. (Part IV). Proceedings of the Zoological Society of London. 1881: 921-952.
Olabarria C. 2005. Patterns of bathymetric zonation of bivalves in the Porcupine Sea Bight and adjacent abyssal plain, NE Atlantic. Deep-Sea Research I. 52: 15-31.


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Record last modified: 22/03/2016