Shell small (3.4 X 2.3 x 1.4 mm), thin, oval to slightly subquadrangular, rather high (45% of length), porcellaneous, translucent white. Anterior slope convex, posterior concave. Base flat, margin simple, fragile. Apex at 90% shell length, bent backwards, retaining protoconch, partially hidden by teleoconch. Sculpture of thin radial riblets, with regularly disposed prominent small pits, 5-6 thinner lines with smaller pits between each pair; clearly marked growth lines. Inner surface nacreous, discontinuous horseshoe-shaped muscle scar. Periostracum cream, spiny, especially towards margin, the long spines emerging from deeper pits, short spines from smaller ones; 5-6 series of short spines between each pair of longer ones; spines are longer near periphery, in section show hollow thin-walled tubules which do not seem to communicate with exterior. Spines less developed in young specimens.
Protoconch (220 x 140 µm) globose, of half a whorl, partially fused with teleoconch. No apical fold or labial thickening, sculpture reticulate. Angle between growth axis of protoconch and longitudinal axis of teleoconch almost 0°.
Radula typical of family. Rachidian tooth variable even in same specimen, with or without a prominent vestigial fold. First pair of lateral elements vestigial, but clearly visible; second and third laterals very similar, both long, narrow, with four exterior cusps, outer one very small; fourth lateral reduced, almost lacking cusp; fifth lateral big, massive, finely striated posterior surface, large terminal cusp, smaller external lateral cusp. Marginals numerous, long, narrow, laterally compressed, each with finely denti-culated cusp; the outer teeth twisted at about mid-length.
Preserved animal hyaline white. Foot oval, anterior margin densely ciliated. Head large, oral lappets wide, snout densely ciliated around central buccal opening. Cephalic tentacles long, right one has copulatory organ (more developed in larger specimens), projecting from internal side of cephalic tentacle, curved, with long seminal groove. Eyes lacking. Mantle border not reaching shell margin, lacking epipodial tentacles. Distal part of prominent gill fold projects from mid-right of the deep pallial cavity; anus under gill.

The shell is variable, mainly in the height-length ratio. Our specimens fit well with the syntypes and the descriptions of Jeffreys (1883b), Dall (1889a) and Marshall (1986).
The holotype of Cocculina conspersa Dautzenberg & Fischer, 1897 is an eroded, subquadrangular, relatively high shell (3.2 x 2.1 x 1.8 mm), apparently with fine concentric growth lines only, but rough at the margins, with flat base, and apex slightly bent to the left, retaining the protoconch. The anterior slope is convex, and the posterior is concave. The inner side shows a horseshoe-shaped muscle scar. The shell closely resembles the syntypes of Coccopigya spinigera in size, shape, rough margins, bent protoconch and muscle scar, and therefore we consider C. conspersa a junior synonym of the former.

Range: Present study: from the Mediterranean area between Catalonia and Mallorca (41° 5.31' N, 2° 10.80' E to 41° 5.6' N, 2° 50.3' E to 40° 6.8' N, 1° 49.9' E to 41° 4.1' N, 2° 53.4' E), and Chafarinas Islands (North Morocco) (first record from Mediterranean). Other records: Iceland (Warén, 1991); between Faroes and Hebrides (Jeffreys, 1883b); Azores (as Cocculina conspersa Dautzenberg & Fischer, 1897); E. United States (Virginia, North Carolina) (Dall, 1889a).
Habitat: Present study: on decaying wood, in tubes of xylophagid Xylophaga praestans and teredinid Bankia carinatay associated with bivalves Idas simpsoni and Idas ghisottii. rarelv with Coccopigya viminensis in same sample, but appears less common in Mediterranean; also with Copulabyssia corrugata in one sample; depth 642-1777 m. Other records: in tubes of Teredo megotara, with Copulabyssia corrugata and Idas argenteus, in pine wood at 943 m (Jeffreys, 1883b); in Teredo-bored wood, with Copu¬labyssia leptalea, 613-1542 m (Dall, 1889a); on wood and whalebone, 300-400 m (Warén, 1991).