Dictyonal structure in Hexactinosa and Lychniscosa
R. E. H. Reid
Parenchymal frameworks of dictyonine Hexactinellida must not be regarded as constructed by tip to tip union of spicules. The basic mode of union, as stated by Zittel, is enclosure of 2 rays side by side in a common siliceous envelope. Other modes of union occur; but union of spicules tip to tip is not a normal occurrence. The formation of 4-sided meshes is not the general basis of construction of the framework, as has formerly been believed; most 3-dimensional skeletons are correspondingly not composed of superimposed layers of meshwork, and instead are structures having fundamentally no stratified basis, or relation to cubic latticework. Correct analysis of structure requires reference to linear dictyonal strands, formed from series of dictyonalia; the most important factor is the way in which these strands are arranged. Hexactinosan skeletons are of 3 main types when judged on this basis, while most Lychniscosa show a structure which is comparable with the commonest hexactinosan type.
This record provided courtesy of AGI/GeoRef.
