. The Cambridge natural history. Zoology; Zoologia Geral. group Lyssacine members the oldest known sponge, Protospongia fenes- trata, of Cambrian age (Salter). As preserved it consists of a single layer of quadriradiate, or possibly quinqueradiate spicules, which, arranged as a square meshed lattice, supported the superficial layer of the sponge (Fig. 101). Whether or not the fossil represents the whole of the sponge-skeleton does not The extraordinary Recepta- culitidae are probably early Lyssacine forms : they are cup- or saucer-shaped fossils, abundant in FIG. 10L— Part of the spec
. The Cambridge natural history. Zoology; Zoologia Geral. group Lyssacine members the oldest known sponge, Protospongia fenes- trata, of Cambrian age (Salter). As preserved it consists of a single layer of quadriradiate, or possibly quinqueradiate spicules, which, arranged as a square meshed lattice, supported the superficial layer of the sponge (Fig. 101). Whether or not the fossil represents the whole of the sponge-skeleton does not The extraordinary Recepta- culitidae are probably early Lyssacine forms : they are cup- or saucer-shaped fossils, abundant in FIG. 10L— Part of the specimen of Pro- . tospongia fe .Silurian and above all in Devonian * strata, and have been " assigned in turn to pine cones, Foramini- fera, Sponges, Corals, Cystideans," and Tunicata. Hinde' brings forward im- portant arguments for retaining them among Hexactinellida. The only elements in the skeleton of the simpler genera, Ischaditcs, are structures comparable to Hexactinellid spicules. The surface of the fossil presents a series of lozenges FIG. 102. -A portion of the forming a regular mosaic. Each lozenge outer surface of a Recepta- -[s the expanded end of one of the rays culitid. Acanthoconia bar- . , „ which the ex- ol a spicule ; it conceals tour rays in one nestrata in the Sedgwick Museum, Cambridge. Nat. size. (After Soiias.). in panded outer rays of the piane tangential to the wall of the cup- spicules are partially de- -1 stroyed, revealing the four shaped lossil, while the sixth ray pro- tangential rays beneath. • fc vertically to the wall jnto the cavity < 3. (After Hinde.) J . * of the cup. In the genus Receptacuhtes itself there is an inner layer of plates abutting against the inner 1 Sollas, Quart. Journ. Gcol. Soc. 1880, p. 362. - Quart. Journ. Gcol. Sue. xl. 1884, p. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrat
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