12 A MONOGRAPH OF THE 



eight lines in length, by not quite two lines in greatest 

 diameter, and the smallest measured four lines in length, 

 and one, greatest diameter. The form and general aspect 

 of the sponge is very like that of a young specimen of 

 L.fstulosa, but the total absence of hispidation, and the 

 very large size of the surface spicula renders them readily 

 separable by the aid of a lens of two inches focus. The 

 surface as well as the whole substance of the sponge is 

 formed by a strong interlacing of exceedingly large trira- 

 diate spicula, the space covered by many of them being 

 quite equal to half the greatest diameter of the sponge. 

 These spicula vary to a considerable extent in their propor- 

 tions, apparently in accordance with the necessities of their 

 situation, and at the surface they frequently have one ray 

 much longer than either of the other two, and in this case 

 the elongated ray usually runs in the direction of the 

 long axis of the sponge; besides these large and strong 

 spicula, there is no indication of surface armature. The 

 internal defensive spicula are not very numerous ; the 

 spicular ray is equally attenuated, and usually not more 

 than about half the length of either of the others. The 

 mouth of the cloaca is composed of a thin membrane 

 strengthened and supported by slender rectangulated tri- 

 radiate spicula, the margin being nearly purely mem- 

 branous. The interstitial membranes are abundantly fur- 

 nished with small equiangular triradiate tension spicula, 

 disposed without any appearance of regularity. 



Genus Leucogypsia, Bowerbank. 



1. Leucogypsia Gossei, Bowerbank. 



Sponge. Massive, sessile ; surface smooth ; oscula ter- 

 minal, slightly fistulose. Pores inconspicuous. Dermal 

 membrane pellucid, furnished with a minute, irregular 

 reticulation of small equiangular triradiate spicula, with 



