Eucytherura parabatalaria n.sp.

Fig. 4 F-J

" Eucytherura cf.? Cytheropteron tetrapteron (Bonaduce, Ciampo & Masoli) " Porter, 1984 *: 153; pI. 9, figs 6,7.

" Eucytherura parabatalaria" Ayress, 1988 *: 585; pI. 20, figs 6- 12.

Etymology. Greek, close. Referring to the close similarity of this species to Eucytherura batalaria n.sp.

Type material and dimensions. Holotype, OS 14083, adult right valve, length 0.33 mm, height 0.19 mm. Paratypes: OS 14084, adult left valve, length 0.36 mm, height 0.19 mm; OS 14085, adult right valve, length 0.34, height 0.17 mm. All specimens from Site 254, core 1, section 3, interval 50-56 cm, Pleistocene.

Type locality and horizon. East Indian Ocean, southern limit of Ninetyeast Ridge, present day water depth 1253 m, DSDP Site 254, core 1, section 3, interval 50-56 cm, Pleistocene .

Diagnosis. A species of Eucytherura with a gently sinuous dorsal margin and two ventral tubercles, the anterior-most subhemispherical with a low longitudinal ridge, the posterior-most elongate and somewhat tumid. L-shaped ridge posterodorsally; Coarsely primarily reticulate, fossae polygonal, and uniformly secondarily reticulate. Whole of ventral surface microreticulate.

Description. Small, elongate sub-triangular in lateral view. Strongly sexually dimorphic: male valves more elongate than female valves. Anterior margin convex, asymmetrical, strongly rimmed, with a strong denticle at mid-height and two shorter downward projecting denticles anteroventrally. Posterior margin short, straight to slightly convex with two denticles, one at each corner. Dorsal margin sinuous, gently convex ahead of mid-third, gently concave behind. Ventral margin biconvex. Moderately thin-shelled and inflated. Tuberculate: well-developed, sub-hemispherical tubercle just anteroventral of centre, bearing a short longitudinal ridge which extends down anterior slope of tubercle. Posteroventral tubercle elongate longitudinally with a low spine midway on posteroventral slope. L-shaped ridge close to margin posterodorsally formed by accentuated mural elements. Coarse primary reticulation over entire lateral surface, fossae polygonal; muri on anterior rim form a continuous ridge, and muri form a smooth border along anterior half of dorsal margin. Uniformly secondary reticulate, primary fossae subdivided into 5 rounded sub-fossae which are sometimes edged by numerous short ingrowing spines. Ventral surface microreticulate. Ventro-Iateral smooth narrow ridge extends from margin anteroventrally across ventral surface. Internal surface of outer lamella with clusters of 4 to 5 normal pores. Other internal features as for genus.

208, core 4, section 4, late Pliocene, J, external lateral view of adult right valve (SD/WPP/335) from DSDP Site 207A, core 3, section 5, Early Pliocene, K, internal view of adult left valve (SD/WPP/340) from DSDP Site 208, core 4, section 4, Late Pliocene, L, internal view of adult right valve (SD/WPPI 339) from DSDP Site 206, core 16, section 3, Late Pliocene; M-O, Hemiparacytheridea vanharteni n.sp., M, external lateral view of adult right valve (holotype, OS 14582) Early Pleistocene, N, internal view of same specimen, 0, external lateral view of adult left valve (OS 14583) Pleistocene; P-R, Hemiparacytheridea mediopunctata (Coles & WhatJey), P, external view of right valve (MA/IP/430) from DSDP Site 254, core 1, section 3, Early Pleistocene, Q, internal view of adult left valve (MA/IP/431) from DSDP Site 254, core 2, section 1, Late Pliocene, R, external lateral view of adult right valve (MA/IP/429) from DSDP Site 254, core 1, section 2, Pleistocene.

Comparisons. This species is most similar to Eucytherura batalaria n.sp, Eucytherura downingae (Coles & Whatley) and the Mediterranean Eucytherura tetrapteron (Bonaduce et al.) . It can be distinguished from the former two species by its lack of spinosity and more extensively distributed ventral microreticulation, and from the latter species by its more regular primary reticulation.

Distribution. Recorded only from the eastern Indian Ocean in the Pleistocene of DSDP Sites 253, 258 and 259, and in the Late Pliocene to Pleistocene of DSDP Site 254.