On the Structure and Affinities of Palaeodiscus and Agelacrinus . Fig-. 11.—View 1 mm. remoTed or 40 sections -^-^ mm. Fig-. 12.—View li mm, remoTed or 60 sections J^ mm. thick. 1904.] Affinities of Palmodiscus and Agelacrinus. 43 The mouth ring is further strengthened by plates, which underlythe mouth-covering plates. These occupy the angles between II andIII and III and IV. The third, which underlies the large mouth-covering plate of the anal inter-radius, completes the mouth ring inthis region. It has been somewhat attacked by solution in both casesexamined. The flooring plates of t
On the Structure and Affinities of Palaeodiscus and Agelacrinus . Fig-. 11.—View 1 mm. remoTed or 40 sections -^-^ mm. Fig-. 12.—View li mm, remoTed or 60 sections J^ mm. thick. 1904.] Affinities of Palmodiscus and Agelacrinus. 43 The mouth ring is further strengthened by plates, which underlythe mouth-covering plates. These occupy the angles between II andIII and III and IV. The third, which underlies the large mouth-covering plate of the anal inter-radius, completes the mouth ring inthis region. It has been somewhat attacked by solution in both casesexamined. The flooring plates of the mouth ring are thicker thanthose of the remainder of the ambulacra. No trace of any platesare to be observed underneath them. This would seem to indicatethat the central part of the ventral region of Agelacrinus was occupiedby a membrane with calcification weakly, or not at all developed. Asimilar appearance has been described in Edrioaster by Forbes andBather. Bather has supposed that by the pulling in of this membranea vacuum would be produced, thus fixing the animal to the sea floor. No trace of any Maclreporite
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectproceed, bookyear1904
