. The Canadian naturalist and geologist. Natural history -- Periodicals. 1865.] BILLINGS—SILURIAN AND DEVONIAN FOSSILS. 195 Receptaculites, only that it is hexagonal. The plates of all the spicula enlarge until all come into contact, and thus an outer tesselated integument corresponding to the ectorhin is formed. In this stage a section through the seed-like body shews an inner integument (or endorhin), and an outer plated integument (or ectorhin), the two being separated and at the same time connected by the pillar-like cylindrical shafts of the spicula representing the tubes of Receptaculite
. The Canadian naturalist and geologist. Natural history -- Periodicals. 1865.] BILLINGS—SILURIAN AND DEVONIAN FOSSILS. 195 Receptaculites, only that it is hexagonal. The plates of all the spicula enlarge until all come into contact, and thus an outer tesselated integument corresponding to the ectorhin is formed. In this stage a section through the seed-like body shews an inner integument (or endorhin), and an outer plated integument (or ectorhin), the two being separated and at the same time connected by the pillar-like cylindrical shafts of the spicula representing the tubes of Receptaculites. The space between the tubes is, according to some authors, filled with a gelatinous silicious matter; but Bowerbank says he did not detect this substance in the specimens examined by him. This little sac or cell is a Receptaculites in miniature, and it is also one of the embryonic stages of a sponge. When we consider that the full grown and adult individuals of many of the long extinct tribes of animals never attained in their structure a more advanced organization than that exhibited by the embryos of orders living at the present day, it does not seem sur- prising that we should find in the palaeozoic rocks a sponge which although often of large size, never became more highly developed, than is the recent genus Spovgilla, when it has only advanced to the sac-like stage above described. It is not intended to assert here positively that Receptaculites is a sponge, or to determine the question of its zoological rank one way or the other, but only to direct attention to such peculiarities in its structure as appear to me worthy of being taken into account in the investigation. Genus Pasceolus, Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Natural History Society of Montreal. Montreal, Dawson
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