A NEW GENUS OF THE HEXACTINELLID SPONGIDA. 231 



bore a special interest to me, as containing a photograph of a new genus and species of 

 sponge — Sclerothamnus Glcmsii, which I perceived had close affinity with Steere's sponge. 

 Then identity at the first glance I certainly did not appreciate, possibly from his evi- 

 dently being a much smaller imperfect specimen, and also doubtless owing to the blurred 

 ill-defined photographic representation of it. A further careful study of his descriptions 

 and close comparison of figures has, however, convinced me that in the said Sclerotham- 

 nus and Denclrospongia, without a doubt, we have the same generic type, and as regards 

 specific distinction between them I am really at a loss to point out differences. A for- 

 tiori, I regard them as identical ; and therefore Dr. Marshall's name to this remarkable 

 form has the claim of priority, and my own will hereafter necessarily be sunk to that of a 

 synonym. Hence Sclerothamnus Clausii, Marshall, =Dendrospongia /Stem*, Murie. The 

 examples on which Marshall founds his description and diagnosis are two odd pieces 

 got in an old cabinet of the Leiden Museum, locality and history unknown. My data, 

 therefore, clears habitat, and in many other respects supplies points wanting in his com- 

 munication. Dr. Marshall, notwithstanding, has observed and figured the " mucronate " 

 character of the glassy fibres, on which Mr. Carter has laid some stress, and he moreover 

 calls attention to certain phenomena connected with the growth and coalescence of the 

 glassy spicular fibre, besides what he regards as monstrous spicula. 



In his ideas upon the relations of the Hexactinellida he constitutes a division Synatj- 

 loed^ — " Das Lumen der Rohren der verschiedenen Nadeln hangt, wie diese selbst, 

 continuirlich miteinander 2usam.n1.en, so dass das ganze Zittergewebe des Schwammes von 

 einen gleichfalls zusammenhangenden Hohrsystem durchzogen ist " — in which the only 

 generic type is Sclerothamnus, whose characters are : — " Zu den zusammenhangenden 

 Zittern gesellen sich als frei bleibende Nadelformen Besengabeln." The single species 

 as yet known, Scl. Olausii, according to him, has the following diagnosis : — " Polyzoisch, 

 buschformig, mit dichotomisch verzweigten, nicht in einer Ebene gelegenen Aesten. Zwei 

 Pormen von Besengabeln. Zitterwork mit Hockerchen besetzt." 



Into his second division Asynatjloidje and its subdivisions, and with his general con- 

 clusions and remarks on the relationships &c. of the Hexactinellida, neither space nor 

 other circumstances permit me herein to enter. 



Appendix. By H. J. Carter, P.R.S. 



With Dr. Murie's description of Dendrospongia Steerii I should hesitate to interfere, even if I were not 

 well acquainted with the general and microscopic structure of the more durahle parts of the sponge itself, 

 such is the descriptive power and truthfulness of the author. 



Professor Steere's specimen is certainly the largest and nohlest instance of the Hexactinellida on record, 

 and from its hranched form contributes to show that the Hexactinellida are subject to the same influences 

 in this respect as those which determine the variation in form and size of all other sponges, which appears, 

 to a certain extent, to be almost unlimited. 



It is not a little remarkable, too, that a similar specimen, only not half so large (16 inches high), should 

 have been deseribed and figured by Dr. William Marshall, of Wiemar (Zeitschrift f. wiss. Zool. xxv. 

 Suppl., 20th November, 1875), just two months before Dr. Murie brought Prof. Steere's specimen to the 

 notice of the Linnean Society. Still more remarkable is it that just nineteen years before this, and before 

 the same society (viz. 17th February, 1857), large fragments of this species should have been uncon- 



