Very polymorphic species, solid, conic in outline, a little bit cyrtoconoid, whorls usually flattened. Base not much convex, umbilicus missing, columella arched with a thickening in the lower part. Spiral sculpture made by cords either flat or not much roundish, narrower than the grooves. The growth striae, present in the grooves as thin lamellae, can be more or less evident according to the area of origin. Peripherical cord not much developed and last whorl sharp-cornered but non careened. The base has 6-8 cords concentric roundish. Mouth subquadrangular. lip sharp. On a ground brown-greenish in colour there are flammulae cither brown or blackish with dots either red or white. The adult specimens average measures are around 10 mm in height.

Diagnostic characters
Much like J. exasperatus but with 8-10 spiral ridges between keel and adapical suture on the last whorl and 7-9 on its base.
Other characters
The apical angle of this shell is greater than in J. exasperatus (p. 116) and the growth lines are usually less obvious. The last whorl and the aperture are both relatively larger. The colour pattern is extremely variable but usually consists of coffee to chocolate brown with cream or white areas of different sizes, the apical region being a carmine red. The brown and white may form broad alternating bands or a chequered pattern. Some shells are nearly all red. Up to 10 mm high, 8 mm broad; last whorl occupies two thirds of shell height, aperture 40-45%
The animal is like J. exasperatus but lacks the red markings of that species.
J. striatus is confined to the Channel Islands (where it is not uncommon), south west England, and perhaps some southern and western Irish localities (in all of which it is rare). The species ranges south to the Mediterranean. The animals live on weeds, especially Zostera, and on stones with Ulva and Codium at L.W.S.T. and to depths of 200 m. The eggs and spawn of this species are said (Robert, 1902) to be indistinguishable from those of J. exasperatus.

All these characters are changeable and follow a clinale distribution from West to East. The morphotype of the Western Mediterranean is J. striatus aequistriatus (Monterosato) which differs from the form type due to a different H/D ratio and to the colour pattern made by thin axial lines on a ground grey in colour. The morphotype of the Eastem Mediterranean is J. striatus elenchoides Issel, 1878, with a surface almost smooth. Spiral cords very flattened and divided by one thin groove. J.striatus fraterculus (Monterosato 1879), common in Gabès Gulf (Tunisia), has got the lightest shell of this kind, whorls a little bit concave and base flattened. J.striatus delpreteanus Sulliotti, 1889, endemic of Lago di Haro (Messina Sicily - Italy), differs from this type having whorls of spiral and base much more convex.

Distribution: common all over the Mediterranean. More or less frequent according to the locality. Habitat: it lives in the infralittoral zone, either among algae or on poseidons under stones. It was found in the coralligenous of the circalittoral zone too.