cy 



^ 



258 EXPLANATION OF THE PLATES. 



"^•^ PLATE VI. Fig. 1, 2, Halichondria Montaguii of the natural size, 

 and its spicula magnified. Fig. 3, Halichondkia infundibuli- 

 FORMis, and Fig. 4, Its spicula. 

 '^ PLATE "VII. Halichondria ventilabrum of the natural size, with 

 its spicula magnified. The figure is from an Irish specimen in the col- 

 lection of R. Ball, Esq. 

 ^ PLATE VIII. Halichondria SIMULAN3. The figures shew its prin- 

 cipal varieties, drawn from specimens sent to me by Dr Scouler of Dub- 

 lin. Fig. 6, the spicula. 

 r/' PLATE IX. Halichondria fucorum witb its spicula. 



PLATE X. Halichondria panicea. Fig. I, The sponge in its pri- 

 mary crustaceous condition. Fig. 2, in its crustaceous and normal 

 state. Fig. 3, In an irregular lobulated and papillary state. Fig. 4, 

 With a looser and more friable texture than is usual. Fig. 5, in its 

 free massive condition. Fig. 6, A section of two oscula to shew how the 

 canals open into them, and the effluent currents. Fig. 7> The orifice 

 of an osculum magnified. Fig. 8, A thin slice of the sponge magni- 

 fied to shew its structure. P'ig. 9i The spicula magnified. 

 PLATE XI. Fig. 1, Halichondria ^gagropila, from a specimen in 

 the collection of Dr Scouler of Dublin. Fig. 2, The spicula. Fig. 3» 

 Halichondria saburrata, and Fig. 4, Its spicula. Fig. 5, Ha- 

 lichondria PANICEA, var. papillaris, and Fig. 6, its spicula. 

 ^ PLATE Xn. Fig, 1,1,1, Halichondria coalita of the natural size, 

 with its spicula magnified. Fig. 2, Hal. fucgrum, investing a por- 

 tion of Plumularia falcata, whence the peculiarity of its form. Fig. 3, 3, 

 Hal. incrustans in its crustaceous state with the spicula. Fig. 4, 

 A piece of a sponge supposed to be the Spongia pilosa of Montagu, but 

 probably a state of Dysidece fragilis. Fig. o, 6, 6, Hal. suberia 

 of the natural size with its spicula viewed with a high magnifier. 

 PLATE XIII. Fig. 1, 2, 3, Halichondria aculeata with its spicula. 

 Fig. 4, 4, Hal. areolata with the spicula. Fig. 5, 5, Hal. in- 

 causTANS with the spicula. Fig. 6, Dysidea fragilis of the 

 natural size from a dried specimen, with various forms of its spicula. 

 The latter are from sketches furnished by J. S. Bowerbank, Esq. 

 Fig. 7» 8, Hal. carnosa with its spicula. 

 PLATE XIV. Fig. I, Halichondria fruticosa, from a specimen 

 which had been washed ashore and lost its organic mucus. Fig. I, a. 

 A small portion of the fibre magnified. Fig. 1, h, The spicula. Fig. 

 2, 2, Hal. seriata. Fig. 3, 3, Hal. sanguinea with its spicula. 

 Fig. 4, Dysidea fragilis in a dry condition. 

 PLATE XV. Fig. 1, Halichondria virgultosa, natural size. Fig. 

 2, A small slice seen through a low magnifier. Fig. 3, 3, The spicula. 

 Fig. 4, 5, Hal. Ficus, from specimens in the collection of Mr Bean. 

 Fig. 6, The .spicula, from a specimen given me by Mr Edward Forbes. 



