On the Structure and Affinities of Palaeodiscus and Agelacrinus . es of the mouth are merelythe flooring plates of the ambulacra. The ambulacra I and V do notmeet in the angle of the anal inter-radius, and consequently the mouthring cannot be completed by these plates. The enlargement of the 42 Mr. W. K. Spencer. On the Structure and [Mar. 22, anal inter-radius has also produced the secondary fusion of radiiI and II, and IV and Vj a phenomenon not confined to Agelacrinus,hut one found commonly in the Pelmatozoa. Jaekel (8, p. 8) has calledattention to this, Diese Verschiebung der Gabelung zwei
On the Structure and Affinities of Palaeodiscus and Agelacrinus . es of the mouth are merelythe flooring plates of the ambulacra. The ambulacra I and V do notmeet in the angle of the anal inter-radius, and consequently the mouthring cannot be completed by these plates. The enlargement of the 42 Mr. W. K. Spencer. On the Structure and [Mar. 22, anal inter-radius has also produced the secondary fusion of radiiI and II, and IV and Vj a phenomenon not confined to Agelacrinus,hut one found commonly in the Pelmatozoa. Jaekel (8, p. 8) has calledattention to this, Diese Verschiebung der Gabelung zwei Strahlen findetaber tiberall bei Pelmatozoen im analen Inter-radius statt, wo sich diePrimarporen, das Parietalseptum und der After zwischen zwei Strahleneinschieben. Dadurch wird die Abgiiederungsstelle der Radien Iund V etwas nach den Seiten verschoben. The calcification of theplates must be secondary to the location of the internal organs, forthese are formed first during ontogeny. Secondary symmetries in theambulacral plates are thus readily accounted Fig-. 11.—View 1 mm. remoTed or 40 sections -^-^ mm. thick.
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectproceed, bookyear1904
