1863.] DR. J. S. BOWERBANK ON THE SPONGILLID^. 449 



ception their absence, one in every three or four being without 

 them ; and the size of the spicula is exceedingly variable, ranging 

 from ^3 inch long and broad to ^^ inch long by y^'S ^°^^ broad. 

 In other respects the spicula in both species are remarkably similar 

 in their characters. If we have recourse to the less constant but (in 

 this case) valuable characters of form and colour, we can scarcely 

 mistake the species, as the dissimilarity in those respects are stri- 

 kingly marked. 



The measurements given by Mr. Carter of those organs, in his 

 valuable paper, are as nearly in accordance with those I have made 

 as they can be expected to be in such a case. 



I have been unable to find any "amorphous siliceous deposit" 

 cementing the spicula of the gemmules together, and a few minutes' 

 boiling in nitric acid effects a complete separation of them from the 

 animal tissues in which they are imbedded. 



I do not think it probable that the species examined by Meyen 

 was the one that has been named after him, but rather that it was 

 our European species Sponyilla fiuviatilis, with the structure of 

 which Mr. Carter (from his residence in India at the time of writing 

 his paper) was not acquainted. 



Spongxlla pltjmosa. Carter, 



Sponge sessile, massive or subramose ; surface hispid. Oscula 

 dispersed, numerous. Pores inconspicuous. Dermal and interstitial 

 membranes aspiculous. Skeleton-spicula fusiformi-acerate, stout. 

 Ovaries semiovoid ; spicula birotulate, disposed in lines radiating 

 from the centre of the ovary ; shaft three to four diameters of the 

 rotulse in length, cylindrical, abundantly spinous ; rotulse externally 

 convex, internally concave, margins irregularly dentate. Sarcode : 

 spicula subsphero-stellate, multiradiate ; radii spinous ; apices pileate 

 or capitulate. 



Colour yellow or green. 



Hab. Freshwater tanks, Bombay {Carter). 



Examined in the dried state. 



I have received three specimens from Mr. Carter of this distinct 

 and well-characterized species : two of them are portions of larger 

 Sponges, they are both yellow and massive, having the upper surface 

 of each with very slightly elevated portions, but exhibiting no ramose 

 projections ; while the third specimen, rather exceeding 4 inches in 

 diameter, is entirely composed of short branches of a bright-green 

 colour, ramifying from a common base. It is therefore apparent 

 that there is a considerable latitude in form and colour in this species ; 

 and in truth the difference in these respects is so great between the 

 last and the first two specimens that a superficial examiner would 

 undoubtedly designate them as distinct species ; while in their organic 

 structures there is no preceptible difference. 



An average-sized spiculum of the skeleton measured -^^ inch long 

 and Ysir ^'i^'^ greatest diameter. 



The greater portion of the ovaries are semiovoid in form ; a i^yt 



Proc. Zoot. Soc— 1863, No, XXIX. 



