Microscopical Society of London. 1003 



fossil to which it appears to be very closely allied. The fossil 

 alluded to is the Sphaeronites tessellatus, the outer surface of which 

 presents a tessellated structure closely resembling this sponge. It 

 must, however, be remarked that there exists much doubt as to the 

 real nature of this fossil ; but as the external appearance of the 

 plates or compartments in it is precisely like that of the recent 

 sponge, and as certain peculiarities of the internal structure are ap- 

 parently to be met with in both, and, also, as the microscopical 

 examination of the outer and inner surfaces of the fossil present 

 appearances which strongly favour the idea of its spongeous origin, 

 Mr. Bowerbank does not hesitate in referring both to one and the 

 same genus. 



A second paper, by the same gentleman, being a " Description" of 

 a new genus of Fresh-water Sponge," was also read. 



The singular and highly interesting sponge, whose description 

 forms the subject of this paper, was found at Tenby, South Wales, 

 by a poor man who collects fresh- water shells to sell to the visitors. 

 It occurs in a large muddy ditch in the vicinity of Tenby, which, 

 although very near the sea, has no communication with it. To this 

 sponge Mr. Bowerbank gives the name of 



Somatispongia ; and its generic and specific descriptions are : — 

 Sponge with a central, round or oval coriaceous body, surrounded 

 by three winged, keratose fibres, which spring from its surface. 



S. pulchella. Sponge free. Body covered with reticulations, the 

 areas of which are depressed, furnished with two mammae opposed to 

 each other either in the long or short axes : in the latter case with a 

 deep sinus intervening. Fibre flexible, reticulations polygonal, with- 

 out interstitial fleshy matter or spicula. 



This beautiful little sponge is more or less of an oval form. It 

 rarely exceeds half an inch in length from one extremity of the 

 fibre to the other, and the central body is about four lines in length. 

 The fibres are of a greenish amber colour, the body partaking of the 

 same hue, but much deepened by its greater degree of density. 

 When denuded of its surrounding fibres, the body appears to be 

 divided into numerous nearly equal-sided polygonal areas, which are 

 most frequently five or six-sided ; from the angles of these reticula- 

 tions the fibrous structure springs, preserving the same form of reti- 

 culation as that of the parent surface. Its internal structure also 

 presents many interesting peculiarities which were fully detailed in 

 the paper. 



