Memoirs of the Museum of Comparative Zoölogy, at Harvard College, Cambridge, Mass . o 370). Tlio iiroterygial of tlic pectoral fins of the Narcaciontidae have numerous joints between theantorbital, ao, and the pectoral arch, /ic/; the Raiidae have comparatively few, most often but a singleone, that is two segments in the pectoral oppcsite the gills, an arrangement gaining in firnniess ofthe disk along the sides of the branchial chamber. Marked variations occur among the genera of Sympterygia, fig. 3 a semicartilaginous mass in front of the skull displaces the rostral

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Memoirs of the Museum of Comparative Zoölogy, at Harvard College, Cambridge, Mass . o 370). Tlio iiroterygial of tlic pectoral fins of the Narcaciontidae have numerous joints between theantorbital, ao, and the pectoral arch, /ic/; the Raiidae have comparatively few, most often but a singleone, that is two segments in the pectoral oppcsite the gills, an arrangement gaining in firnniess ofthe disk along the sides of the branchial chamber. Marked variations occur among the genera of Sympterygia, fig. 3 a semicartilaginous mass in front of the skull displaces the rostral cartilage; inMalacorhina the rostral cartilage is lacking and the forward part of the skull is much like that of theDasybatiflac. In general the hyobranchials are reduced, but the copula, hbr, is complete and notsegmentetl as in Dasybatidae nor divided as in Narcaciontidae. The scapular, sc, overlaps the prominent lateral prepelvic processes recall similar ones on the fossil genus Cyclobatis. Mem. Mus. Comp. 2o6l., Vol. 36. Plagiostomes. Plate 68. .v|). chl(.

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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1913