Bolivina sp. A

Hanagata, S & Nobuhara, T, 2015, Illustrated guide to Pliocene foraminifera from Miyakojima, Ryukyu Island Arc, with comments on biostratigraph, Palaeontologia Electronica (Cambridge, England) 33 (8), pp. 1-142 : 71

Bolivina sp. A

Figures 22.25, 22.26

Description. Test very small for the genus, less than 0.2 mm in length; shape typical of genus; periphery rounded; sutures slightly depressed and strongly curved towards periphery; surface almost smooth with fine perforation; aperture interiomarginal but inside of aperture invisible due to sediment fill.

Remarks. This small species may not be detected in studies using sieves of 120-mesh or larger. We cannot find any species to assign this form to; we refrain from erecting a new species since it does not show enough characters to discriminate it from the vast amount of established bolivinid species.

Occurrence. Sporadic in the Onogoshi, Yonahama, and Minebari formations.

Figures

FIGURE 22. Family Bolivinidae. All scale bars = 0.1mm. 1, 2. Bolivina antiqua d'Orbigny, 1: MPC-26140, 2: MPC- 26141, both from sample 18 (Oura Formation,?PL1). 3—6. Bolivina cacozela Vella, 3: MPC-26142 from sample 2-2 (Minebari F., PL5); 4: MPC-26143 from sample 5 (Minebari F., PL5); 5: MPC-26144 from sample 10 (Onogoshi F., PL2); 6: MPC-26145 from sample 16 (Yonahama F., PL3). Specimens of 3 and 4 have larger test size than those of 5 and 6. 7, 8. Bolivina glutinata Egger, 7: MPC-26148 from sample 15 (Yonahama F., PL3); 8: MPC-26149 from sample 16 (Yonahama F., PL3). 9, 10. Bolivina retia Oki, 9: MPC-26154, 10: MPC-26545, both from sample 4 (Minebari F., PL5); 9.4, moisturized specimen showing internal septa. 11, 12. Bolivina robusta Brady, 11: MPC-26155 from sample 5 (Minebari F., PL5); 12: MPC-26156 from sample 10 (Onogoshi F., PL2). 13, 14. Bolivina striatula Cushman, 13: MPC-26157 from sample 14-2 (Yonahama F., PL4); 14: MPC-26158 from sample MK01 (Yonahama F., PL2). 15, 16. Bolivina variabilis (Williamson), 15: MPC-26161 from sample 16 (Yonahama F., PL3); 16: MPC-26162 from sample MK01 (Yonahama F., PL2). 17, 18. Bolivina cochei Cushman and Adams, 17: MPC-26146, 18: MPC-26147, both from sample MK01 (Yonahama F., PL2). 19, 20. Bolivina kiiensis Asano, 19: MPC-26150 from sample 3 (Onogoshi F., PL1); 20: MPC-26151 from sample 3-2-low-silt (Onogoshi F., PL1). 21, 22. Bolivina pacifica Cushman and McCulloch, 21: MPC-26152 from sample 1-2 (Minebari F., PL5); 22: MPC-26153 from sample MK01 (Yonahama F., PL2). 23. Bolivina cf. subspinescens Cushman, MPC-26159 from sample MK01 (Yonahama F., PL2). 24. Bolivina cf. yabei Takayanagi, MPC-26163 from sample MK01 (Yonahama F., PL2). 25, 26. Bolivina sp.A, 25: MPC-26164 from sample 11 (Onogoshi F.,?PL1); 26: MPC-26165 from sample 16 (Yonahama F., PL3). 27. Bolivina translucens Phleger and Parker, MPC-26160 from sample 5-2 (Minebari F., PL5).