910 PBOCEEDINGS OF THE NATIONAL MUSEUM. tol.xxii. 



* Cameronia coni])lanata Bourouignat, Uu. et Ir. Tan., 1886, p. 76. Lake Tan- 

 ganyika. 



* Cameronia dromauxi Bourguignat, Un. et Ir. Tan., 1886, p. 84. Lake Tan- 



ganyika, 



* Cameronia giraudi Boukguignat, Nat. Prod., 1885, p. 107. Lake Tanganyika. 



* Cameronia r/uiUerneti Bourguignat, Un. et Ir. Tan., 1886, p. 72. Lake Tan- 

 ganyika. 



* Cameronia jouherti BouiiGUiNAT, Un. et Ir. Tan., 1886, p. 88. Lake Tan- 

 ganyika. 



*" Cameronia lavigirina Bourguignat, Un. et Ir. Tan., 1886, p. 85. Lake Tan- 

 ganyika. 



* CaMie/'owift Zoea)-(?m?ui Bourguignat, Un. et Ir. Tan., 1886, p. 78. Lake Tan- 

 ganyika. 



* Cameronia marioniana Bourguignat, Esp. Onk., 1885, p. 28. Lake Tanganyika. 



* Cameronia mahilUana Bourguignat, Un. et Ir. Tan., 1886, p. 86. Lake Tan- 

 ganyika. 



"Cameronia moineti Bourguignat, Un. et Ir. Tan., 1886^ p. 89. Lake Tan- 

 ganyika. 



* Cameronia pulcliella Bourguignat, Un. et Ir. Tan., 1886, p. 73. Lake Tan- 

 ganyika. 



* Cameronia obttisa Bourguignat, Un. et Ir. Tan., 1886, p. 75. Lake Tanganyika. 



* Cameronia randebeli Bourguignat, Un. et Ir. Tan., 1886, p. 90. Lake Tan- 

 ganyika. 



* Cameronia revoiliana Bourguignat, Moll. Tan., 1885, p. 107. Lake Tanganyika. 

 ^Cameronia vynckii Bourguignat, Un. et Ir. Tan., 1886, p. 81. Lake Tan- 

 ganyika. 



Genus MONOCONDYL^^A d'Ortaigny, 183S. 



(Type, MonocondyUea Paraguay ana A' Or\)\g\iY.) 



Aplodon Spix (not of Eaflnesque, 1818), Test. Fluv. Bras., 1827, pi. xxv, figs. 1, 2. 

 Monocondylam d'Orbigny, Guerin Mag., 1835, p. 37. 

 Spixoconcha Pilsbry, Nautilus, VII, 1893, p. 30. 



Shell rounded to obovate, rather solid, with a low, posterior ridge 

 which is generally bordered by two or more dark, radiating bands; 

 epidermis dull olive green to olive brown, cloth like; hinge with two 

 irregular teeth under the beak in the left valve and two in the right, 

 the posterioi- under the beak, the anterior in front of it and interlocking 

 with those of the left valve, the whole generally more or less tuberculate; 

 nacre soft, silvery, with iridescent shades ; anterior scars united ; pos- 

 terior indistinct; prismatic layer wide. 



Animal with the marsupium occupying the whole length of the inner 

 branchicTB ; gills very large, curved below, inner very much the larger, 

 united the whole length of the abdominal sac; palpi small, round below, 

 attached along their upper edge; mantle thick, greatly thickened at 

 the edge, with a few papillae in front of the branchial opening below; 

 branchial opening large, with numerous small knob-like papilla?; anal 

 opening large, without papilhTe, separated completely from the branchial 

 opening by a bridge; superanal opening not closed below. 



(Group of Monocondylcea guarayana.) 



Shell obovate, inflated, solid, often slightly produced just behind the 

 center of the base; beaks full, turned inward and forward. 



