The Quarterly journal of the Geological Society of London . part 3] THE KELESTOMIX-E 209 (fig. 5). The last condition is never attained by the Kelesto-minae; but both Kelestoma and Morphasmopora have abundantintereecial secondary tissue with elongate lacuna?, and, in Mor-phasmopora jukes-brownei, these elongate lacuna?, whether in theform of long slots or very much lengthened triangles, take ona curved or wavy shape, and often simulate the apertures ofavicularia. Fig. -i. — Diagram representing a Fig. 5. — Diagram showing a still further development of the further development of secon- conditi
The Quarterly journal of the Geological Society of London . part 3] THE KELESTOMIX-E 209 (fig. 5). The last condition is never attained by the Kelesto-minae; but both Kelestoma and Morphasmopora have abundantintereecial secondary tissue with elongate lacuna?, and, in Mor-phasmopora jukes-brownei, these elongate lacuna?, whether in theform of long slots or very much lengthened triangles, take ona curved or wavy shape, and often simulate the apertures ofavicularia. Fig. -i. — Diagram representing a Fig. 5. — Diagram showing a still further development of the further development of secon- conditioii representedin fig. 3. dary tissue (black) which now The secondary tissue (black) completely fills the intereecial has increased in amount. valleys^ and has no median lac a The behaviour of the Kelestomine avicularia also is have seen that the sporadically-distributed, indifterently-orientated, blunt-apertured avicularia of the Primitive Pelma-toporid became the definitely-placed and definitely-orientated,somewhat acute-apertured avicularia of the Primitive Kelesto-mine. The numbers are fixed at four, in two pairs, in connexionwith the aperture of every normal cecium; and, of these pairs, themore proximal is placed in the intereecial tissue just beside theproximal pair of apertural spines, and the distal pair just distalto them. During evolution, the proximal pair are sooner or laterdiscarded, and the distal pair become raised on long pillar-likepedestals that keep at about the same height as the fusion of theproximal apertural spines with the fused distal forks of the aper-tural bar, and form with them the proximal shield of the secondary 210 DR. W. D. LANG ON [vol. lxxi\> aperture. There is always, however, a deep cleft between thesepe
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