. Polycystins, figures of remarkable forms &c. in the Barbados chalk deposit (chiefly collected by Dr. Davy, and noticed in a lecture delivered to the Agricultural Society of Barbados, in July, 1846) . abilis, on Taf. III. of Professor MaxSchultzes Beitrage, &c. 4.—A transparent Plate, irregularly three-lobed, each lobe bifurcate,in slide Barbados. Material from Dr. Kingsley. Itappears to be of the nature of those Hex-radiate plate-spicules depicted by Dr. Bowerbank as from a EuplecteUa. 5.—All explanation of mode of growth of fig. 5 on PI. VII. A Dicty-ochus net ? 6.—^A Rhabdolithes, giv
. Polycystins, figures of remarkable forms &c. in the Barbados chalk deposit (chiefly collected by Dr. Davy, and noticed in a lecture delivered to the Agricultural Society of Barbados, in July, 1846) . abilis, on Taf. III. of Professor MaxSchultzes Beitrage, &c. 4.—A transparent Plate, irregularly three-lobed, each lobe bifurcate,in slide Barbados. Material from Dr. Kingsley. Itappears to be of the nature of those Hex-radiate plate-spicules depicted by Dr. Bowerbank as from a EuplecteUa. 5.—All explanation of mode of growth of fig. 5 on PI. VII. A Dicty-ochus net ? 6.—^A Rhabdolithes, giving a curious example of the way the siliceousoutshooting sjiines seem to go wandering on wherever tlieyfind the least obstruction; at a there seems to have been anintended change of course, checked. The extreme fiexibilityof these spines might lead to .a supposition whether there mightnot be combined with the silex in their composition some por-tion of the keratede (or horny matter) stated by Dr. Bowerbankto enter into the formation of even the siliceous coating of thespines. 7. A double circlet of Acanthodesmia of Miiller. A single circlet is given on PI. II, fig. 6. Barbados !TY PLATE 1.—A magnificent spicule, probably of some unknown sponge; but as,on careful examination of the beautiful figures of Dr. Bowerbankand Professor Max Schultze (kindly lent by Dr. Gray) noneappear identical, it is introduced here to exemplify its approachin character to some of the Polycystip spines (or sjjicules) inslide 48. Chimborazo, Barbados. Dr. Davy. 2 & 3.—Polyeystins, the whole of whose siliceous shells appear to berunning out into spines, simulating, or asserting, their relation-ship to sponge-spicules. Barbados. 4.—A broken s])ine of a Polycystin ? highly magnified, shewing theconstruction, and that the fine tliorn-like secondary spicules are really points of support for, or commencements of, the sili-ceous net-work of the shell. Barbados slide, 102. 5.—^T
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