A treatise on zoology . have in preceding pages been spoken of as del-toids (A). They meet close around the mouth like the A of manyBlastoids, and in Ilyhocrinus and Carabocrimis they show traces ofhydrospires of Codaster type. On the other hand, they arehomologised, and justly so, with five similar plates that occur inCoccocrinus, Si/mhafhncrinns, Fisocrinus, Allagecrinns, Mijrfillocrinus, some Platycrini, and the specimen ofTaxocrinus intermedins (Fig. XXXVII.)described by AVachsmuth & Springer(Nov. 1888). In most of thesegenera the orals (or A) cover themouth, and the food-grooves pass inun
A treatise on zoology . have in preceding pages been spoken of as del-toids (A). They meet close around the mouth like the A of manyBlastoids, and in Ilyhocrinus and Carabocrimis they show traces ofhydrospires of Codaster type. On the other hand, they arehomologised, and justly so, with five similar plates that occur inCoccocrinus, Si/mhafhncrinns, Fisocrinus, Allagecrinns, Mijrfillocrinus, some Platycrini, and the specimen ofTaxocrinus intermedins (Fig. XXXVII.)described by AVachsmuth & Springer(Nov. 1888). In most of thesegenera the orals (or A) cover themouth, and the food-grooves pass inunder them; but in Taxocrinus themouth is open, and the grooves withambulacrals pass between the orals ;while in Hijhocrinus and Carahocrinusthe ambulacrals rest on the edges ofthe apposed orals, showing that the Tegmen of Taxocrinus intermedins. grOOVeS Were actually above those A, anal ridge; J>r, edges of brachials; ^, , illAinh, illlAinb, iiiteraiiibula- of first, second, and third onler iAmb. iDlAmb - NiUAmb IKi. XXXVII. 0, five orals a little distance fVon. From this primitive Pakeozoic type, the peristome. (After Wachsinuth & three HuCS of CVOlutioU Start : (1)Springer, ) a i i ^1, 1 f .U Aml)uiacra pass over the edges ot theorals, while ambulacrals and sometimes interambulacrals graduallycover the orals, which seem thus to sink below the surface and todiminish in size ; the posterior oral, however, usually remains largeand is pierced by hydropores, while the increased size of the anal tubepushes it more towards the oral centre {ejj. Easpirocrinus, Cijatho-crinus, Cnpressocrinus, Figs. XXXVIII., XXXIX.). (2) And)ulacniand ambulacrals pass between the orals, leaving an open mouth,while the orals gradually atro])hy {ejj. Taxorrinns, Fig. XXXVII.,I)robably other Palaeozoic Flexibilia, and certaifily many of theirNeozoic descendants). (^) Ambulacra pass beneath the orals,and gradually also beneath other tegminal ])lates, which aredevelope<l /Kfri
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