1927] Pilsbry-Bequaert, The Aquatic Mollusks of the Belgian Congo 157 
tened, usually thickened and frequently toothed at the aperture. Operculum cal- 
careous, paucispiral with excentric nucleus ; 1ts inner edge as arule with projecting 
processes (apophyses) articulating with the columella. 
Animal living in fresh, brackish, or salt water. Head large; rostrum divided and 
lobed in front. Tentacles long and slender; the eyes sessile or pedunculate, placed at 
the external bases of the tentacles. Foot short and broad, truncate before and obtuse 
behind, the sides simple. Respiration branchial ; the gill large, triangular, pointed, 
free at its extremity. Branchial and excretory orifices on the right side. No external 
male organ. Radula of the rhipidoglossate type: a single small central which is some- 
times absent; normally 5 laterals of which the inner ones are sometimes vestigial and 
the two outer ones are frequently fused into a capituliform or umbrella-shaped plate; 
numerous marginals (uncini) which are narrow, ligulate. 
Of the three subfamilies into which H. Burrington Baker! has. 
recently divided this family, the Smaragdine are not known to occur in 
Africa. 
Neritinz 
Eyes pedunculate. Radula: unpaired central present; inner lateral large, 
transverse, not inclined more than 45 degrees; the two middle laterals vestigial; 
the two outer laterals united into a capituliform complex which bears on its inner side 
a well-marked, Y-shaped thickening; the marginals with elongate blades. Operculum 
in most cases with marginal projections and a curved rib and a peg on the inner side. 
This subfamily is represented in the Ethiopian Region by the genera 
Neritina Lamarck, Theodozus Denys de Montfort, and Nerita Linneeus. 
Nertia is truly marine and easily distinguished by its heavy, calcareous 
shell, without epidermis. One species, Nerita senegalensis Gmelin, is 
found on the coast of the Atlantic near the mouth of the Congo (San 
Antonio, Banana, Moanda). 
NERITINA Lamarck 
Neritina Lamarck, 1816, ‘Encyclop. Méthod., Vers,’ II, Pl. cccctiv; 1822, 
‘Hist. Nat. Anim. sans Vertébres,’ VI, 2, p. 182. Type by designation of Children 
(1823): Nerita pulligera Linneus. 
Laphrostoma RAFINESQUE, 1815, ‘Analyse de la Nature,’ p. 144.2 
Clypeolum R&cxivz, 1850, Journ. de Conchyl., I, p. 144. Type by designation of 
H. B. Baker (1923): Nerita pulligera Linneus. Not Clypeolum Récluz, 1842. 
Shell solid, hemispherical or subglobose, with short spire. Columella flattened 
and straight, smooth or finely denticulate. Lip acute, smooth within. Operculum 
semi-circular, large enough to close the aperture completely, with well-developed 
apophyses on its inner surface; usually both an inwardly projecting peg and a 
subspiral or arched rib. 
1M{. Burrington Baker, 1923. ‘Notes on the radula of the Neritide.’ Proc. Ac. Nat. Sci. Philadel- 
hia, LX XV, pp. 117-178, Pls. rx—xv1. ; yee 
4 Pa. was based upon ‘‘ Neritina Lamarck,’’ which was not introduced into binomial nomen- 
clature until 1816, though Lamarck had used the vernacular “ Néritine without mentioning a species 
in 1809 (‘Philosoph. Zoolog.,’ I, p. 321) and 1812 (‘Extrait du Cours de Zoologie,’ p. 117). As Rafines- 
que referred to a genus which had not been named at the time, his substitute may well be considered a 
nomen nudum. 
