Pneumoderma atlanticum pacificum

Pneumoderma atlanticum (Oken, 1815) subsp. pacificum (Dall, 1871)


This is a relatively large naked pelagic snail, about 2.5 cm long. It is oval, with a slightly transparent, usually pigmented skin. The wings are well developed, the posterior footlobe is long. The buccal mass has two lateral arms each with up to 50 suckers. It lives in the Pacific Ocean, in the upper water layers and is never abundant (Pneumoderma a. pacificum).

Taxonomic Description

The body is subcylindrical, elongated and rounded anteriorly. When alive, the animal is purple. The head parts are whitish. Wings subquadrate, arched at their inner anterior margin, deeply notched at their inner posterior edge. Anterior margin with a well marked band of white, remainder dull purple and lighter posteriorly. Head indistinct, cylindrical, with two small short posterior tentacles. The acetabuliferous arms are triangular with about 50 small suckers each. The radula formula, in specimens of 10 mm, is 4-0-4. The hook sacs are very deep. The lateral footlobes form a cardiform body, purple with a black spot. The median footlobe is linguiform. The gills are small. The lateral gill is fringed, with lateral somatic crests. The posterior gill has four radiating crests with simple, well marked fringes.
Body length up to 25 mm.


A special description is not available.


This form is a protandric hermaphrodite.


This form is a carnivore.


It is restricted to the N-Pacific Ocean, see the Pneumoderma a. pacificum map.


Pneumodermon pacificum Dall, 1871: 139.
Types not found in USNM.
Type locality: 37°8'N 136°10'W, Coll.: Dall, reg. no. 301.