A treatise on zoology . Dorsal fins, with tlie eiuioskeleton exposed, of: A, NotUlaiins (Heptaitchtts) ciiiereus, Gin. ;B, (ringlymostoma clrmtum, Gm. ; C,Zygaena nwlleas, Risso ; D, Ehynchobatus djedde>;!is, Forslc.(After Mivart.) ;, anterior radials lying on vertebral column ; , anterior radial ; b,longitudinal basal; , basal ; , distal segment of radial; /, fin web supported by ceratotrichia ;;, median segment of radial; ; posterior radial; , proximal segment of radial. Thesefigures illustrate the formation of basals by the concrescence of Fui.
A treatise on zoology . Dorsal fins, with tlie eiuioskeleton exposed, of: A, NotUlaiins (Heptaitchtts) ciiiereus, Gin. ;B, (ringlymostoma clrmtum, Gm. ; C,Zygaena nwlleas, Risso ; D, Ehynchobatus djedde>;!is, Forslc.(After Mivart.) ;, anterior radials lying on vertebral column ; , anterior radial ; b,longitudinal basal; , basal ; , distal segment of radial; /, fin web supported by ceratotrichia ;;, median segment of radial; ; posterior radial; , proximal segment of radial. Thesefigures illustrate the formation of basals by the concrescence of Fui. 49. Left-side view of a portion of the tail of Raja. The vertebi-al column has been exposed infront, also the en<loskeleton of the two dorsal fins, showing the concrescence of the radials attlieir base to form a posterior axis. necessary to assume this even on Gegenbaurs theory, which derivesthe fin-skeleton from originally separate gill-rays. The objection often raised that, in Elasmobranchs, the fin-radials PAIRED FINS 77 become differentiated in a continuous procartilaginous rudiment(Balfour [28], Kuge [337a]), and not as separate rudiments, appliesequally to the median fins (Balfour, Braus [50, 176]). More-over, in Teleosts, and possibly in many other fish, the radials areseparate from the first (Harrison [197]). It is also urged that themetamerism of the radial muscles of the adult fin does not correspondto that of the embryo (Braus [50]). Now, although it may be true
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Keywords: ., bookcentury1900, bookdecade1900, bookpublishe, booksubjectzoology
