Encentrum valkanovi Althaus, 1957

This typical species (Fig. 30) is characterized by its dorso-ventrally flattened body with large and broad anterior pseudosegment showing longitudinal folds, the wide apart-set toes, and the 2 close-set light-refracting globules displaced to the right at the posterior of the brain. The specimens seen fit the original description, except for some details: the toes are more drawn-out and more or less distinctly offset near mid-length; the ‘ovate structure’ in the toes consists of a light-refracting spherical reservoir and part of its supply canal; the 4 dorsal longitudinal folds on the anterior trunk segment are 2 double-folds; the ‘spine’ between the toes is a rounded caudal papilla with projecting cilia.

Encentrum valkanovi was not uncommon in the sublittoral of all areas studied, from 50 m up to 8 km off shore, and depths of 15‒40 m, June, July, August, September, water temperature 17−25 °C. To date the species was only known from sublittoral psammon of the Black Sea, Varna, Bulgaria (Althaus 1957).

Redescription of trophi by SEM. Trophi (Figs 30 D, 31) of subgenus Encentrum type. Trophi large, elongate, fairly slender. Rami outline longer than wide, ratio length:width of closed rami 1.8−1.9; dorsal outer margin of rami weakly concave laterally, angular posteriorly; ventral outer margins with shallow carina rami (Figs 31 C, E: cr) near 3/7 from apical ramus tip; median rami opening elongate drop-shaped; subbasal chambers dorsally with small depression medio-caudally from basifenestrae; basifenestrae dorsal, small, ellipsoid; subbasifenestrae caudal, small, rounded. Each ramus with single, slightly offset apical tooth set at right angle to trophi axis; cardal apophyses very small. Prior to apical teeth a preuncinal tooth set at a right angle to trophi axis; preuncinal teeth with elongate triangular head and short shaft forming obtuse angle; head with small cardal apophysis. Fulcrum longer than ramus, in dorsal/ventral view distal end slightly widening; distal widening indented dorsally, with median prominence ventrally; in lateral view with broad base, quickly tapering, continuing parallel-sided. Unci medium long, slightly curved, head shorter than shaft, with dorsal and ventral apophyses; dorsal and ventral ribs fairly broad. Intramallei long, sock-shaped, with relatively long, rounded medio-lateral basal expansion bearing opening medio-caudally; inner side expanded, fitting lateral concavity of rami. Supramanubria absent. Manubria slightly less incus length, stout, rod-shaped, proximal half straight, distal half incurved with crutched cauda, head short, triangular.

Measurements. Body (N=5): total length 180‒210 µm, toe 28‒35 µm; trophi (N=5): length 24‒26 µm, ramus 8.5‒9.8 µm, fulcrum 11.6‒11.7 µm, uncus 5.6 µm, preuncinal tooth 2.4 µm, intramalleus 4.8×3.7 µm, manubrium 18.2‒18.7 µm.