Caecum Fleming, 1813

Vannozzi, Angelo, Pizzini, Mauro & Raines, Bret, 2015, Revision of South African Caecidae (Mollusca: Gastropoda), African Invertebrates 56 (1), pp. 99-99 : 100-101

Genus Caecum Fleming, 1813

Type species: Dentalium trachea Montagu, 1803 (by subsequent designation, Gray 1847: 203) from the Atlantic coasts of Europe, the Mediterranean Sea and northwestern Africa.

Key to South African Caecum species. The key applies to adult, well-preserved specimens. Periostracum characters are not taken into consideration.

1 Septum with mucro .................................................................................................2

– Septum without mucro..........................................................................................15

2 Mucro pointed, more or less central........................................................................3

– Mucro marginal.......................................................................................................4

3 Tube slender, tapering; septum narrow with flat ventral profile ................ chinense

– Aperture oblique; septum large with convex ventral profile................. lindae sp. n.

4 Macula large with a frosted appearance..................................................................5

– Macula small or absent............................................................................................7

5 Tube cylindrical, twisted, mucro clearly rotated toward the right side..................... ........................................................................................................... intortum sp. n.

– Tube subcylindrical, not or barely twisted ..............................................................6

6 Aperture strongly oblique, septum dome-shaped with an ear-like, right-oriented mucro............................................................................................ knysnaense sp. n.

– Aperture with a rather well­developed swelling, septum almost flat with a dorsal nail-like mucro ...................................................................... austrafricanum sp. n.

7 Aperture with a clear swelling ................................................................................8

– Aperture with a barely developed swelling or without it......................................10

8 Septum dome-shaped with dorsal mucro .............................................. cf. gulosum

– Septum on the cutting plane, mucro rotated toward the right side..........................9

9 Mucro broad, right-oriented............................................................... morgan sp. n.

– Mucro narrow................................................................................... cf. musorstomi

10 Tube small (length <2 mm)..................................................................................11

– Tube large (length> 2.5 mm)................................................................................14

11 Tube with microsculpture......................................................................................12

– Tube without microsculpture.................................................................................13

12 Tube evenly arched, aperture simple, microsculpture composed of incised collabral grooves ............................................................................................... incisum sp. n.

– Tube slender, microsculpture composed of longitudinal worm-like incisions.......... ............................................................................................................. maraisi sp. n.

13 Septum subquadrate in lateral view, mucro right-oriented ............... subquadratum

– Septum dome-shaped with a rounded, almost dorsal mucro.................. inhacaense

14 Tube colourless, semitransparent, with several small rings, more visible in the abapical half of the tube ......................................................................... leilae sp. n.

– Tube whitish, opaque, with some strong rings before aperture; microsculpture composed of several wavy longitudinal threads ............................ neocaledonicum

15 Sculpture formed by strong, well­defined rings....................................................16

– Scupture weak or absent........................................................................................17

16 Sculpture formed by 20–25 strong rings, septum flat on the cutting plane............... ............................................................................................................... sepimentum

– Sculpture formed by smaller and more numerous rings, often missing in central portion of tube ...................................................................................... cf. oahuense

17 Tube smooth with some rings before aperture ........................................ succineum

– Tube smooth without sculpture or microsculpture................................. cf. glabrum