668 MEMOIRS OF THE CARNEGIE MUSEUM. 



EXPLANATION OF PLATE XLVIL 

 Left gills of Diplodon deceptus (Simpson), Castalla nehringi Von Ihering, 



AND right gills OF MONOCONDYL^A LENTIFORMIS LeA AND AnODONTITES 



clessini (Fischer); twice natural size; inner gill to the left, 

 outer gill to the right (Figs. 1-4). 



Horizontal sections of gills of Diplodon hasemani Ortmann, Diplodon imitator 



Ortmann, and Diplodon decipiens Ortmann ; much enlarged ; inner 



gill to the left, outer gill to the right (Figs. 5-7). 



Fig. 1. Diplodon deceptus (Simpson), from Rio Jacuhy, Cachoeira, Rio Grande 

 do Sul, Brazil. Carn. Mus. Cat. 6L5868. Gille of female (No. 9). 



Fig. 2. Castalina nehringi Von Ihering. from Rio Tiete, Itapura, Sao Paulo, Brazil. 

 Carn. Mus. Cat. No. 6L5120. Gills of half-grown female (No. 1). 



Fig. 3. Monocondylcea lentiformis Lea, from Rio LTruguay, LTruguayana, Rio 

 Grande do Sul, Brazil. Carn. Mus. Cat. No. 6L5841. 



Fig. 3a. Gills of male (No. 1). 



Fig. 36. Gills of female (No. 4). 



Fig. 4. Anodontites clessini (Fischer), from Rio Vaccahy-mirim, Santa Maria, 

 Rio Grande do Sul, Brazil. Carn. Mus. Cat. No. 6L5820. 



Fig. 4a. Gills of male (No. 12) (Shell of this specimen figured on Plate XLI, fig. 4, 



and Plate XLII, fig. 1). 



Fig. 46. Gills of female (No. 11) (Shell of this specimen figured on Plate XLII, 

 fig. 2). 



Fig. 5. Diplodon hasemani Ortmann, from Rio Guapore, near Rio Sao Simao, 

 Matto Grosso, Brazil, Carn. Mus. Cat. No. 61.5857. Section of gills of gravid female 

 (No. 5). 



Fig. 6. Diplodon imitator Ortmann, from Rio Vaccahy-mirim, Santa Maria, Rio 

 Grande do Sul, Brazil. Carn. Mus. Cat. No. 61.9284. Section of gills of female (No. 

 33) (Shell of this specimen figured on Plate XXIV, fig. 7). 



Fig. 7. Diplodon decipiens Ortmann, from creek (tributary to Rio Iguassu), Ser- 

 rinha, Parana, Brazil. Carn. Mus. Cat. No. 61.9253. Section of gills of gravid female 

 (No. 5). 



