448 — Bulletin American Museum of Natural History [Vol. LIII 
Etherea ScHWEIGGER, 1820, ‘Handb. d. Naturgesch. der Skel. Ungeglied. Thiere, 
p. 708. £. elliptica Lamarck cited. 
Aitheria group Caillaudiana Bourcutenat, 1880-1881, ‘Matér. Moll. Aceph. 
Syst. Europ.,’ I, p. 68. Monotype: theria caillaudi Férussac. 
Aitheria group Niloticiana BouRGUIGNAT, 1880-1881, op. cit., p. 65. Type by 
present designation: EH. elliptica Lamarck. 
Aitheria group Chambardiana Bourcuienat, 1880-1881, op. cit., p. 69. Mono- 
type: A. chambardi Bourguignat. 
Aitheria group Letourneuxiana BoURGUIGNAT, 1880-1881, op. cit., p. 69. Type by 
present designation: Atheria petrettinia Bourguignat. 
Shell irregular, inequivalve, oyster-like, covered with a dark periostracum, 
attached by either valve; beaks anterior, that of the fixed valve often lengthened. 
Interior nacreous but rather dull, usually blistered or cellular. Hinge without teeth; 
ligament thickened inwardly posteriorly, forming a resilium, terminated by a deeply 
entering, narrow sinulus. Two large adductor impressions. 
ayy et 
y/ 
Ss 
BOLLE NS alee SAK, 
Ly 
oe LS KGL 
COL LX) 
. ) E/) 
ee LB 
to 0 200 ago 600 80 (000 Miles. 30 
20 0 =m 4008 a / 
49 SO 60 70 
Meridian o of Greenwich 
Map 6. Distribution of the genus Etheria. 
Ltherva is confined to the Ethiopian Region and Madagascar (Map 
6). The widely spread continental species, EZ. ellintica, has been taken 
also in the Mahavavy and Androtsy Rivers, northwestern Madagascar. 
