A Monograph of the British Spongiadae (Volume 3) (Paperback)

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: PLATE V. Leuconia Nivea, Grant. Vol. ii, p. 36,' Mon. Brit. Spongiadse;' vol. i, pi. rxviii, figs. 351, 352. The external characters of this species vary to a very considerable extent in different localities. Exposed to the full action of the sea on the under surfaces of thin ledges of rock, as at the neighbourhood of Scarborough, it appears as a thin coating sponge, with the orifices of the cloacse scarcely elevated above the common surface of the sponge, as represented by fig. 1, of the natural size, in the present volume. In more sheltered situations it has still more or less of a coating form, but is furnished with a series of irregular ridges or crests, on which the excurrent orifices of the cloacse are situated, as represented by fig. 2, Plate V, of the present volume, of the natural size. In caves or other well- sheltered localities it assumes the form of congregated lobular masses, as represented by fig. 352, vol. i,' Mon. Brit. Spongiadee,' of the natural size, and by fig. 351 in the same plate, which represents a longitudinal section of one of the mammse form, portions exhibiting one of the cloacal cavities of the sponge and its internal defensive spicula. X 50 linear. Figs. 3, 4, 5 represent the large, stout, equiangular, spiculated, triradiate, internal, defensive spicula. X 80 linear. The basal radii of fig. 5 are projected backward in tripodal fashion. Very minute specimens of this form are also found in the lining membrane of the cloaca, one of which, X 660 linear, is represented by fig. 89, plate iv, vol. i, 'Mon. Brit. Spongiadae.' Figs. 6, 7 represent two of the equiangular, triradiate, skeleton spicula. X 80 linear. Fig. 8.?One of the unicurvo-cruciform, tensionspicula of the lining membrane of the cloaca. X 130 linear. Leuconia Fistulosa, B...