452 Bulletin American Museum of Natural History [Vol. LIII 
Madagascar. Its occurrence in Lake Tanganyika appears very doubtful. 
We can find no definite records from Lake Nyasa or from within the 
Zambezi system. 
This species has been recorded from many localities in the Belgian Congo: Falls 
of the Congo (mut. nidus hirundinis and mut. tubulifera; Pechuel-Loesche Coll. and 
O. Baumann Coll.). Kwango River and at its confluence with the Kasai River 
(elliptica and tubifera; R. Bittner Coll.). Nyangwe in the Lualaba River (tubifera; 
Wissmann Coll.). Between the Lulua and Lualaba Rivers (trigonula; Wissmann 
Coll.). Uele River (bourguignati and semilunata; du Bourg de Bozas Coll.). Yam- 
buya in the Aruwimi River (tubifera; Schubotz Coll.). Confluence of Larger Lu- 
bembe River and Luapula in about 12° S. (elliptica)?; Kalengwe in the Lualaba River 
(bourguignati); Kibombo in the Lualaba River (cailliaudi) (J. Bequaert Coll.). 
Leverville; Kwilu River; northern bend of the Congo from Lisala to Basoko (ellip- 
tica; F. M. Dyke Coll.). E. v. Martens has also recorded the var. catlliaudi from the 
Chiloango River near Landana. According to the junior author’s experience LH. 
elliptica occurs in practically every fair-sized river of the Congo basin, but he has not 
seen it in Lake Edward nor in the estuary below Zambi. At the Congo Museum 
Tervueren, there are also specimens, both of typical elliptica and the var. cailliaudt, 
from Kasenga in the Luapula River (Stappers Coll.). The species also occurs in the 
Lubumbashi River near Elisabethville. 
Congo River at Stanleyville; Faradje in the Dungu River (Lang 
and Chapin Coll.). Luapula River at Kasenga (L. Stappers Coll.). 
Specimens of the race tubsfera from the Dungu River reach a length 
of about 140 mm. In most of them both valves, when not adnate, bear 
tubular spines, but sometimes they are lacking on one (the left) valve. 
One of the Stanleyville lot is figured (Pl. XLVI, figs. 1-1a). 
The forms described as bourguignat: and heteromorpha mut. tubu- 
lifera appear to be merely tubzfera. 
Dr. Simroth described two forms, to which he applied three names, 
from the Congo Falls. They are thus defined: 
Aitheria heteromorpha (1894). Of moderate size. Epidermis thick, 
internal layer iridescent. Either right or left valves attached to stones. 
Two very different forms: | cS 
Mutation: tubulzfera (1894). Lower valve flatter, upper excavated, 
provided with tubules. 
Mutation: nzdus herundinis (1890). Lacking tubules; lower valve 
excavated, angulate, the upper flat. 
The mut. tubulifera appears to agree fully with the examples before 
us which we refer to EL. elliptica tubifera. The mut. nidus hirundinis is 
‘The Tanganyika record rests upon an old, dead specimen sent by E. C. Hore and supposed to be 
from Ujiji, and another, also dead, from somewhere on the eastern shore. The late Dr. Stappers did not. 
collect the genus in the lake. 
_ 27 his is the southernmost definite record on the continent. 
