Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum . on of the clasper is a continuation, in the median axis, of thebasipterygium of the fin, and is composed of two groups of cartilages, the basalgroup (including the basipterygium) and the terminal group. [a] The basal group (fig. 2) Ishiyama has pointed out, that in Japanese rajids, the basal group is notspecies specific, and, although White (1937) has proved that the number ofproximal segments and other cartilages in the basal group tend to vary in largegroups of the elasmobranchs, the basal group may only be used in
Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum . on of the clasper is a continuation, in the median axis, of thebasipterygium of the fin, and is composed of two groups of cartilages, the basalgroup (including the basipterygium) and the terminal group. [a] The basal group (fig. 2) Ishiyama has pointed out, that in Japanese rajids, the basal group is notspecies specific, and, although White (1937) has proved that the number ofproximal segments and other cartilages in the basal group tend to vary in largegroups of the elasmobranchs, the basal group may only be used in phyleticconsiderations among the batoid fishes. Examination of the basal group ofR. rhizacanthus seems to support this view, since the same seven cartilages arepresent as in the Japanese rajids (see Ishiyama, fig. 7). The basal group in R. rhizacanthiis consists of the basipterygium, andbj and bg cartilages, the Beta-cartilage, and the axial cartilage, which extends RAJA RHIZACANTHUS REGAN AND RAJA PULLOPUNCTATA SMITH 5OI basipterygium b^ cartilage ?^;;;^\ > fin fays. axial Fig. 2. Raja rhizacanthus. Cartilages of the basal group of theclasper. to the terminal part of the clasper, and is covered by the dorsal and ventralmarginal cartilages (fig. 2). The basipterygium is a short, stout structure, towhich are attached in a groove on its lateral margin, the last 6 fin rays of thepelvic fin. Distally, the basipterygium is elongated on its dorsal surface toform a protuberance which overlaps the bj cartilage. The proximal end of thebi cartilage is visible from the dorsal side, but the Beta-cartilage, situateddorsally to the b^ and bg cartilages, completely obscures the bg cartilage andthe distal end of b^. The Beta-cartilage is more or less flat, serving as a regionof attachment for the m. flexor internus, but is slightly thickened and upraisedat its proximal end, forming a shelf The distal ends of the ba and Beta-cartilage are superimposed so that bothof these elements play a par
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectnaturalhistory, booky
