South American Naiades : a contribution to the knowledge of the freshwater mussels of South America . becomes a secondarywater-tube (PI. XLVIII, fig. 7b). 3. Non-marsupial gills (Fig. 3, o) also with septa and water-tubes, but thesepta less strongly developed and without a ridge. 4. Inner lamina of inner gills entirelyconnected with abdominal sac (South Ameri-can forms), or free from it (African forms). 5. Palpi nearly semicircular, longer thanhigh, with a short posterior truncation,strongly curved lower margins, and indis-tinct posterior jwints (Fig. 3, h). 6. Larva supposed to be a lasidium(
South American Naiades : a contribution to the knowledge of the freshwater mussels of South America . becomes a secondarywater-tube (PI. XLVIII, fig. 7b). 3. Non-marsupial gills (Fig. 3, o) also with septa and water-tubes, but thesepta less strongly developed and without a ridge. 4. Inner lamina of inner gills entirelyconnected with abdominal sac (South Ameri-can forms), or free from it (African forms). 5. Palpi nearly semicircular, longer thanhigh, with a short posterior truncation,strongly curved lower margins, and indis-tinct posterior jwints (Fig. 3, h). 6. Larva supposed to be a lasidium(according to Von Ihering). The shell generally has no beak-sculp-ture whatever. In very rare cases a traceof concentric sculpture has been observed(see under Anodontites trapezea). Hinge-teeth more or less obsolete, reduced in num-ber, or size, and very often entirely absent (Anodontine type of hinge). Dorsalmuscle-scars mostly absent in South American forms, very rarelj^ a faint traceseen, or a few are present, as in Leila. In African forms, there is one single well-developed dorsal Fig. 3. Diagram of soft parts of female ofAnodontites patagonica rubicunda (Lea). Nat-ural size, left section of mantle removed, a,Anal opening; b, Branchial opening; h, Palpi;i, Inner gUl; a, Outer gill; p, Pes; t, Union ofmantle separating anal and branchial openings. Subfamily Remarks. Shell of various shapes, subelliptical, subtrapezoidal, subovate, suborbicular,or sub triangular, sometimes more or less alate. Beak-sculpture mostly present,rarely missing, but often indistinct or obliterated by erosion, always of the radialtype, with two sets of radial ridges, starting from two points, immediately in frontand immediately behind the tip of the umbo, and extending to a varying degreeupon the disk. The posterior ridges of the anterior set, and the anterior ridges ofthe posterior set, generally interfere with each other in the middle of the disk, ortmann: south
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Keywords: ., bookcentury1900, bookdecade1920, bookidsouthamerica, bookyear1921
