"Gulella" radius (Preston, 1910)

Rowson, B, Warren, B. H. & Ngereza, C. F., 2010, Terrestrial molluscs of Pemba Island, Zanzibar, Tanzania, and its status as an " oceanic " island, ZooKeys 70, pp. 1-39 : 20

28. "Gulella" radius (Preston, 1910) Figs 60-61

Ennea radius Preston 1910: 529; pl. VII, fig. 8

Notes.

As noted by Verdcourt (1985) there is either substantial shell variation in the species Ennea radius Preston, 1910, or it comprises a complex of related taxa. This cannot be resolved without a thorough revision. Preston’s (1910) type from the Shimba Hills is said to be 3.25mm high and is strongly acuminate. Verdcourt (1985) figured a specimen from Diani Beach, Kenya which is much less acuminate but measures 4.23mm (calculated from his drawing). At up to 5.45mm, Pemba specimens are larger still, but resemble the type in being strongly acuminate and with less tumid whorls than the Diani Beach material. Specimens referred to Gulella radius from Unguja ( Rowson 2007) are small (to 3.0mm) and not strongly acuminate. The peristomal teeth are in the same basic pattern in each of these populations, but vary in their size and complexity, none being quite as different as some of the other nominal species (discussed in Rowson and Lange 2007). What does appear relatively constant is the size, shape, and sculpture of Pemba specimens, which occur throughout the island (Table 2). They may form an island taxon worthy of subspecies or species status, which is given consideration in the discussions on endemism in the present paper. Recent systematic work ( Rowson 2010) indicates "Gulella" radius does not belong in the genus Gulella L. Pfeiffer and a genus-level revision is in progress.