All forms have in common a medium (5 to 10 mm) size for the genus, a moderately high spire. The aperture is oval-rounded, with an inner lip closely appressed in the adult, flush to the surface of the preceding whorl without any umbilicus or chink. The radular morphology within the group is rather homogeneous, as no consistent diagnostic features have been found to differentiate the subspecies. Only the insular subspecies give slight radular differences which do not justify separate descriptions.

Radular morphology
The central tooth is characterized by subparallel anterior and posterior margins, and a rounded outline on each side. The first pair of laterals terminates with a strong stout conical cusp (rather elongate in T. pullus canarica) and bears 3 to 5 other similar cusps decreasing slightly in size to wards the inner side (almost equal in T. pullus azorica). There is moreover an outermost cusp which is characteristically reduced in size.
The next two pairs of laterals are also terminated by a strong conical cusp, but there are usually no more than 1 to 3 other cusps on the inner side and one or (rarely) 2 — 3 on the outer side, not so reduced as in the first pair.
The first 3 pairs of laterals are of grossly similar size, whereas the two next decrease in size. These also terminate with a stout conical cusp, flanked by one (occasionally two) smaller ones on each side.
The marginals are imbricated in the first 4—6 rows. The first pair is characteristically smaller than the next one and may bear one (occasionally 2—3 in T. pullus azorica) digitations on its inner side. The pectinate structure is achieved by the 10th to 15th row.

Shell morphology. Measurements up to 9 x 6 mm, with 5.5 whorls. General shape moderately high, Whorls regularly rounded. Surface smooth and glossy, with indistinct growth lines. Shell material porccllanous in adult shells. Extremely fine spiral microsculpture may be seen under favourable conditions only. Aperture oval-rounded. Inner lip closely apprcsscd without any umbilicus or chink in adult shells. Colour pattern. Colour pattern normally includes dark red and/or brown flames and dots on a white to brownish or reddish background. Most commonly, there are brown flames starting shortly below the suture, and crescentic patches of similar colour arranged spirally on the lower part of the whorl. The remainder of the surface is occupied by regularly-displayed dots, these normally reaching the lowermost part of the last whorl next to the columella. The relative importance and positions of these elements vary to a great extent, and one or another (dots, flames, etc) may occupy the whole surface. Rare colour patterns may be black flames on whitish background throughout; two braided spiral red bands on white background; white; etc.

Diagnostic characters
Shell glossy, solid, with conical spire more or less straight-sided; whorls slightly tumid; operculum hemispherical and calcareous externally. Colour very variable but usually with erratic pattern of reddish spots and streaks.
Other characters
There are 5-6 whorls, apparently smooth but with delicate growth lines and spiral lines more obvious near the apex. The aperture lies in a gently prosocline plane and is slightly oval. The outer lip arises below the periphery of the last whorl and is thin, a little turned out at the base; the inner lip usually forms only a glaze over the last whorl. The colour pattern is extremely variable: the shell may be pale cream, golden, carmine red, or chocolate brown, all without pattern, but usually there is a mottling or striping of red and cream. Up to 10mm high, 5mm broad; last whorl occupies 80% of shell height, aperture about 50%.
The snout is rather small, the cephalic tentacles long, slender, and fringed with sensory papillae, each with a lateral eye stalk. Both neck lobes have a fringed edge. The foot is narrow, its anterior and lateral edges double, and there is a longitudinal groove along the sole. There are three pairs of epipodial tentacles. Flesh yellowish, but greenish on eye stalks and mantle edge; there are red-brown lines along the head, the sides of the cephalic tentacles and the foot.
T. pullus extends north from the Mediterranean to the western parts of the Channel, all Irish coasts and the west coast of Britain to the Orkneys: absent from the east Channel and the North Sea. It is found near L.W.S.T. on rocky shores and to depths of 35 m. It is most abundant in rock pools and on the small red weeds on which it feeds. Breeding may occur all the year round. Fertilization is external as the orange eggs escape from the mantle cavity. A larva hatches after about 10-12 hours, settles after 2-5 days at a shell height of about 1.1mm, mainly on the small red weeds on which adults live (Fretter, 1955; Fretter & Manly, 1977b).

This is the subspecies living in the Mediterranean, distinct from the other subspecies: picta, canarica and azorica at Atlantic distribution. Species smaller than tenuis and speciosa, solid, not much slim, surface bright. Outline globose, ovoidal, whorls convex, the last one of which really large. Suture broad, aperture round in form, external lip sharp, columella a little bit arched. Columellar margin particularly adorned. Also this species is really variable in colour pattern: light red is often predominating. Ornamentation made by several pits either red or brown in colour, close, interrupted by axial flammulae undulating and interrupted, in several colours. There are often present some wide spiral bands in different colours. Operculum calcareous, a little bit spiral, convex externally, dirty white in colour. In literature, for this species too, there are a lot of varieties in colour, all of them without any value. Average measures of adult specimens are around 8-9 mm in height.

The nominal subspecies as intended here is best characterized by a solid shell, rounded whorls and a general predominance of dots and flames in the coloration. Unlike the Atlantic subspecies, the chromatic pattern of the adult shell cannot be seen by transparency inside the aperture except on the edge of the outer lip, and the interior appears uniformly whitish.
The Black Sea representatives of the group have been distinguished by Milaschevich (1909) as Phasianelta pontica. They are mostly characterized by a high frequency of oblique patterns in their polychromatism, in a way that somewhat recalls T. pullus picta. Shell material and shape are otherwise as in Mediterranean T. pullus pullus. According to A.V. Grossu (in Hit.), their separation as a subspecies is not necessary and they will be thus included in the synonymy of T. pullus pullus.

In our opinion, this taxonomic complex should account for all the forms described by Nordsieck (1973) under Tricotia s.str., Tricolia (Tricoliella) and Tricolia (Tricolietta).
The Mediterranean T. pullus pullus has been retained as the nominal subspecies, according to Linnaeus' type locality "in M. Mediterraneo" and in good agreement with the widespread conception of T. pullus s. str. (e.g. Bucquoy, Dautzenberg & Dollfus, 1884 = B.D.D.).
However, the polytypic T. pullus group does not amount merely to a series of geographical subspecies. A complication arises with T. tenuis, a form well defined and clearly separable from sympatric T. pullus pullus in most parts of the Mediterranean, but transitional alike to T. pullus picta in the western-most Mediterranean. Thus, T. tenuis cannot be treated as a subspecies notwithstanding its belonging to the T. pullus group.

Classification of the insular forms T. pullus canarica and T. pullus azorica as subspecies of the continental T. pullus or as distinct species cannot be but a subjective decision, due to their allopatric geographical ranges. It is true that insular specimens can be recognized as such from their morphology, but the differences do not seem sufficient to treat them as species. A distinct feature of insular subspecies is reduced variability.

The nominal subspecies is reported throughout the Mediterranean. On the coasts of Sicily, Northern Africa, Balearic Islands and overall towards the Straits of Gibraltar, morphology and polychromatism may be transitional to T. pullus picta . Habitat is infralittoral, on algae or on Posidonia grounds.

Habitat: it lives on laminariae in the infralittoral zone.
Distribution: it can be found all over the Mediterranean. Quite common.