Microcystina minima ( Adams, 1867 )

Muratov, Igor V., 2010, Terrestrial molluscs of Cabo Delgado and adjacent inland areas of north-eastern Mozambique, African Invertebrates 51 (2), pp. 255-255 : 277-278

Microcystina minima ( Adams, 1867)

Fig. 46

Macrochlamys minima: Adams 1867: 303 , pl. 19, fig. 2 (near Port Louis, Mauritius; c. 1.3× 0.5 mm).

A single shell was found on Cabo Delgado.Previously known only from the Mascarene Islands where it is quite common and recently recorded from Zanzibar (Rowson et al. in press). The smallest species in the study area. Can be easily distinguished from the following species by the lack of spiral sculpture.

The shell was originally described “... depressa, discoidea ... Diam. 1⅓, alt. ½ mill.” and the apex is not visible on the original illustration. The measurements in the original description were clearly approximate. Griffiths and Florens (2006: 130, pl. 27, fig. E) illustrated M. minima with a protruding apex and gave “Diameter: 1.3 mm; height 0.5 mm ” for the size of the shell. However, if calculated from the proportions of that illustration, assuming that diameter is 1.3 mm, the height of the shell would be 0.82 mm. Thus, in view of the fact that there are no other shells with a narrow umbilicus, without any spiral sculpture and 1.3 mm in diameter found so far on Mauritius, it would be safe to assume that M. minima has variably protruding apical whorls.

Figures

Figs 46–52. Euconulidae:(46) Microcystina minima, 0.68×1.20 mm, stn 7; (47) Afroguppya rumrutiensis, 1.3×1.9 mm,stn 7; Helicarionidae:(48)“Sitala” jenynsi, 10.5×16.0 mm,stn 12; (49) Trochonanina albopicta, 7.5×11.5 mm,stn 5; (50) T.bloyeti, 5.8×12.0mm,stn 17; (51) Trochozonites crenulata, 9.3×12.0 mm, subadult, stn 7; (52) Quickia concisa, 6.0×3.9 mm, stn 7. Scale bar 1 mm in Figs 46–47; 5 mm in Figs 48–52.