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Show 126 DR. J. S. BOWERBANK ON SPONGES. [Feb. 13, Family 8. Phakelliadee. The author, in endeavouring to vary the mode in which I have described the genus Phakellia, states that the *** skeleton is formed of closely reticulated horny fibres, forming an expanded mass," &c. This is incorrect, as it is not a kerato-fibrous sponge, but belongs to the order Silicea. See Mon. Brit. Sponges, vol. i. p. 186. Family 10. Polymastiadce, p. 503. "Sponge with tubular fistulous branches; tubes open at the end, and formed of longitudinal and transverse fascicules of fibres." Here, again, the author has fallen into a great error in describing the "fistulous branches" as open at the end. In no species of Polymastia that I have ever seen is that the case. See Mon. Brit. Sponges, vol. ii. p. 73. Family 12. Euplectelladce, p. 504. "Skeleton composed of longitudinal, transverse, and oblique bundles of spicules intersecting each other, and forming a network." This description of the structure of the skeleton of Euplectella, Owen, as I have before stated, is incorrect, the whole skeleton being truly siliceo-fibrous. Family 13. Esperiadee, p. 504. "Sponge massive. Skeleton composed of fusiform and linear spicules, interspersed with anchorate, bihamate, or birotulate spicules. Sarcode soft." The description of this family is singularly incomprehensible. " Sponge massive." This character would apply to by far the greater number of sponges in existence. "Skeleton composed of fusiform and linear spicules." All the four primary forms of skeleton-spicula are liable to fusiformity; which of the four forms does the author mean, any one in particular or all of them ? And when he names "linear," what form of linear spiculum does he mean? as all straight or slightly curved spicula are linear. " Interspersed with anchorate, bihamate, or birotulate spicules." This embraces a most extensive field of investigation, as we shall presently see. " Sarcode soft." All sponge-sarcode is soft. Thus it will be seen that every one of the characters assigned by Dr. Gray to the Esperiadee are singularly indefinite. Subsequently, at page 532, he divides the family into six sections, which are about as ill-defined as the characters of the family. In the first place, the author designates all the retentive spicula as defensive spicula. The defensive spicula, external and internal, are quite another class of spicula than those peculiar to the sarcode. See Mon. Brit. Spong. vol. i. p. 21. The application of the retentive, or bihamate and anchorate, spicula to the distinction of families or genera is peculiarly unfortunate. I will not trace their occurrence through the exotic genera of sponges, but confine myself to their range among the British genera. They are met with in Microciona, Hymedesmia, Hyme-niacidon, Halichondria, Lsodictya, and Desmacidon-six genera, containing 126 species; and of this number of species, 51 only have their spicula imbedded in their sarcode ; and it rarely occurs that a species has only one form, and frequently three forms are present mixed together. Family 14. Tethyadee, p. 504. The author describes the ske- |