- 1927] Pilsbry-Bequaert, The Aquatic Mollusks of the Belgian Congo 163 
4 
Neritina (Alina) oweniana “Gray”? DaAvUTZENBERG, 1921, Rev. Hopl Aine, TX, 
p.. 158: 
Neritina (Neripteron) oweniana Wood. H. B. BakeErR, 1928, Proc. Ac. Nat. Sci. 
Philadelphia, LX XV, p. 142, Pl. x, fig. 8 (radula). 
Nefuku on the creek of anaes at the mouth of the Congo (type locality of N. 
hessei; P. Hesse Coll.). 
This species is known on the west coast of Africa from Cape Palmas to Angola. 
Zambi and Malela, in the estuary of the Congo (H. Lang and J. 
Bequaert Coll.). Several hundreds of specimens. 
This depressed, auriculate neritine has a network of black on an 
ecru-olive or rarely isabella-colored ground. The network varies in 
_ coarseness of mesh, and is often interrupted by one to three light bands. 
The ventral callus varies in color from iron gray to orange cinnamon or 
light pinkish cinnamon with some gray stains or suffusion; the smooth, 
toothless columellar edge is pale or white. The apex is sometimes eroded 
into a deep pit. The outline is variable, especially in degree of develop- 
ment of the posterior lobe of the lip. The convexity of the whole shell 
varies widely. The spire is normally very small, but in rare individuals 
in which the Juvenile form is continued into the adult stage it is rather 
prominent. 
Several of the specimens from Zambi bear the lower valves of hatched 
eggs and also a few unhatched eggs. These are elliptical or. subcircular 
in outline and their greatest diameter varies from 1 to 2.3mm. Mogquin- 
Tandon! noted that the eggs of Theodoxus fluviatilis are enclosed in a 
thick, coriaceous, resistant shell; the egg itself, he says, is globular, 
opaque, and white. The young mollusk would have difficulty in hatch- 
Ing, were it not that about that time the shell divides into two valves 
after the fashion of a dehiscent fruit, one of the valves dropping off while 
the other remains on the support. The egg-shells of N. oweniana appar- 
ently have a similar structure. Moquin-Tandon states that the egg- 
shell of 7. fluczatilis is more or less caleareous, but in the case of N. 
oweniana the dehiscent valves seem to be chitinous, since they do ant 
effervesce with oxalic acid. 
The young stages have a more normal NV wipes and coloration. 
There is a black lineolation with numerous clear spots outlined with 
black, and two spiral series of opaque, light spots near the periphery. 
The operculum is peculiar by having a semicircular ridge at the 
base, concentric around the peg. 
N. oweniana attains its fullest development in nearly fresh water, 
above the mangrove belt, as at Zamb1. 
11852, Journ. de Conchyl., ITI, p. 26. 
