on^^ Dorvillia agariciformis. 211 



show in common the characteristic agaricine contour, and 

 vary from all hitherto described Tethyadge in the possession 

 of the dependent fascicles of long anchoring spicula by means 

 of which it rests secure on the treacherous surface of the 

 yielding ooze which constitutes its habitat. Dr. Bowerbank 

 has thought fit to assume that these dependent fascicles are 

 " skeleton-fasciculi of the sponge drawn out of the basal por- 

 tion " at the time of his supposed mutilation, an error of 

 judgment only explicable by his over-anxiety to identify the 

 species with his own. On equally slender grounds, because 

 he cannot find them in his own example, he considers himself 

 justified in condemning as " extraneous " in mine certain very 

 characteristic three- and four-rayed tension-spicula of the sar- 

 code, figured and alluded to in my description (M. M. J. 1870, 

 pi. Ixvi. figs. 16-18 and p. 294). Since perusing his comments 

 I have reexamined carefully mounted sections of the sponge, 

 and am perfectly satisfied as to the correctness of referring 

 these spicula to the position already indicated, which again 

 constitutes valuable evidence in support of its being a species 

 perfectly distinct from Dr. Bowerbank's. It is also most 

 satisfactory to remark that Prof. Wyville Thomson has de- 

 tected these same types of spicula in his specimens and figured 

 them in his unpublished plates, which have again been repro- 

 duced in Dr. Oscar Schmidt's ' Spongienfauna des atlantischen 

 Gebietes,' where they may be readily recognized at pi. vi. 

 fig. 12. The anchoring filaments in Prof. Thomson's speci- 

 mens exceed mine in length and abundance. 



The nomenclature of this sponge, which has proved itself 

 a very " apple of discord " among spongologists of the day, 

 will now admit of definite solution. Allowing, with Oscar 

 Schmidt, that the character of the dependent anchoring fila- 

 ments, in which it differs from all Tethyce hitherto described, con- 

 stitutes a modification and adaptation to its natural habitat, 

 scarcely justifying its being promoted to the rank of a distinct 

 genus, the generic title of Tethya is still retained, with the 

 specific one of agariciformis already bestowed upon it by Pro- 

 fessor Wyville Thomson and myself, the following being 

 offered as a brief summary of its technical characters already 

 more comprehensively treated of in the two journals here 

 quoted. 



Tethya agariciformis^ Kent. 

 Dorvillia agariciformis^ Kent, Monthly Microscopical Journal, December 



1870, p. 293, pi. Ixvi. (excepting figs. 10-12, 14, 15, & 19) ; Ann. & Mag. 



Nat. Hist. Jan. 1871, vol. vii. ser. 4. p. 37. 

 Tisiphonia agariciformis, WyviUe Thomson, MS. Porcupine Exp. 1870. 

 SteUata agariciformis, Oscar Schmidt, Spongienfauna des atlantischen 



Gebietes, p. 08, pi. vi. fig. 12, 1870. 



