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Show 1868.] DR. J. S. BOWERBANK ON SPONGES. 127 leton in this family as " consisting of simple filiform spicules, with three prongs or three recurved points at the outer end." This is inaccurate. The skeleton of Tethea cranium, Johnston, which the author has selected as the type of his family, is composed of simple fusiformi-acerate spicula, the fusiformi-porrecto-ternate and fusiformi-recurvo-ternate ones being purely external defensive spicula (Mon. Brit. Spon. vol. ii. p. 83). The Genera. Haying discussed the general principles of Dr. Gray's new systematical arrangement of the sponges in his classes, orders, and families, we will now proceed to consider the mode in which he proposes to establish his numerous new genera ; and it will perhaps facilitate our comprehension of his scheme if we first consider the present condition and numbers of the genera in contrast with the characters and numbers of Dr. Gray's new series of them. The author proceeds in the first place to adopt to a considerable extent the genera established by previous writers on the Spongiadse, altering the phraseology according to his own ideas of terminology, sometimes omitting, as in his character of Stematumenia (p. 511), the most distinctive character of the genus, the fibro-membranous tissues, and then adding a variety of characters derived from the specific ones of the type species of the genus he adopts, thus completing the heterogeneous mixture of descriptions. In this mode the author has adopted sixteen genera from Professor 0. Schmidt's 1 Die Spongien des Adriatischen Meeres,' twenty-nine from my * Monograph of the British Sponges,' and seven others from various authors, making a total of fifty-two genera. The number of genera treated of in Dr. Gray's paper is 157, so that we have a total of 105 new genera proposed to be established ; and these, we shall find, are based upon the descriptions of species hitherto comprised in the genera of the authors quoted above, with alterations to suit the occasion. And, finally, others are founded on the descriptions of single spicula, described in the anatomical portion of vol. i. of m y 'Monograph of British Spongiadse' as examples of organic form, without the slightest knowledge on his own part of the sponges whence they were derived. In the construction of his families, we have seen that the course pursued by Dr. Gray has been that of appropriating every known genus within his reach, without the slightest consideration of the different and perhaps discrepant principles on which they have been based by their respective authors. The same mode is adopted by him in his proposed new genera. Every species having a determinate specific character is at once seized upon by Dr. Gray, and converted into a new genus; and it seems to matter little to him whether the specimen the characters of which are thus appropriated be in his own possession or the property of a private collector, as, in the latter case, it is surreptitiously taken, without the least regard to the owner of the specimen, or |