Ditreta Biernat, 1973

Holmer, Lars E. & Biernat, Gertruda, 2002, Urban and Peri-urban small and medium-size Enterprise Development for sustainable Vegetable Production and Marketing Systems, Acta Palaeontologica Polonica 47 (1), pp. 141-156 : 152

Genus Ditreta Biernat, 1973

Type and only species: Ditreta dividua Biernat, 1973 .

Diagnosis.—See Biernat (1973: 65).

? Ditreta dividua Biernat, 1973

Fig. 9 .

? Ditreta dividua sp. nov.; Biernat 1973: 66, pl. 5: 1–8.

Holotype: ZPAL Bp XV /37h; ventral valve (W = 6.0, L = 1.6).

Type locality: Wysoczki. Holy Cross Mountains, Poland.

Type horizon: Tremadoc chalcedonites.

Material.—Total of 1 dorsal and 1 ventral valve. Figured ventral valve: RM Br133818 (W = 1.47, L = 1.13, H = 1.06); dorsal valve: RM Br133817 (W = 1.33, L = 1.03, WI = 0.56, LS = 0.83).

Remarks.—This species is poorly understood, and the new material includes only two specimens that appear to be similar to those described by Biernat (1973). The specimens cannot be referred with certainty to D. dividua , but they are similar in having a rounded shell with a straight posterior margin and a widely conical ventral valve. The ventral apical process is poorly preserved. The dorsal valve is also similar to that of D. dividua in having fairly well−defined cardinal muscle scars, and a low dorsal median ridge.

Figures

Fig. 9. A–F.?Ditreta dividua Biernat. A, D. Dorsal valve RM Br133817, interior (A, × 36), detail of pseudointerarea (D, × 80). B, C, E, F. Ventral valve RM Br133818, oblique lateral view (B, × 32), exterior (C, × 30), oblique posterior view (E, × 30), detail of larval shell (F, × 165). All specimens from the Tremadoc chalcedonites, Wysoczki.