Memoirs of the Museum of Comparative Zoölogy, at Harvard College, Cambridge, Mass . 0. PLATE 70. POTAMOTRYGONIDAE. Fig. 1-2. ciRcuLARis. M. C. Z. 295 (Page 419). Fig. 3—1. Disceus Z. 606 (Page 426). 1, 3. Dorsal view. 2, 4. Ventral view. The River Trygons are olose allies of the Dasybatidae. They have no rostral cartilage from theskull forward, the copula, hbr, is sogmented, the jjropterygial basalia of the jjeetoral fins, pap, are .strongand in a single piece between the antorbital and the shoulder girdles, and the postliranchial , pbs,is reduced. Disceus, fig.

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Memoirs of the Museum of Comparative Zoölogy, at Harvard College, Cambridge, Mass . 0. PLATE 70. POTAMOTRYGONIDAE. Fig. 1-2. ciRcuLARis. M. C. Z. 295 (Page 419). Fig. 3—1. Disceus Z. 606 (Page 426). 1, 3. Dorsal view. 2, 4. Ventral view. The River Trygons are olose allies of the Dasybatidae. They have no rostral cartilage from theskull forward, the copula, hbr, is sogmented, the jjropterygial basalia of the jjeetoral fins, pap, are .strongand in a single piece between the antorbital and the shoulder girdles, and the postliranchial , pbs,is reduced. Disceus, fig. 3, has a small hardly distinct antorbital cartilage, ro, a broad postspiracularpsp, a wide bar in the shoulder girdle and short orbital ; Potamotrygon, fig. 1, has a largerantorbital, a narrow and elongate postspiracular, a narrower bar in the girdle and longer orbital both genera the are more or less solidly anchylcsed. Disceus has elongate narrowo])ercular cartilages, op 1-5. i Mem. Mus. Comp. Zool., Vol. 36. Plagiostomes. Plate hlti: phr \)Ct.

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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1913