GRANTIA. 183 



pressa. These three kinds of spicula are likewise calcareous, 

 and dissolve with rapid effervescence on being touched with di- 

 luted nitric acid. On looking closely into the surface of the ^S*. 

 nivea, with a single lens, we perceive that the large triradiate 

 spicula lie parallel with the surface, and contribute to form and 

 protect the pores." Grant. 



Mr M'CoUa has furnished me with a variety from the Irish 

 coast that merits to be distinguished. The sponge rises up in 

 compressed sinuous leaf-like lobes, which are united together so 

 as to form a lobulated crust nearly an inch in thickness, with a 

 circular osculum on every projecting angle. (Plate XX. Fig. 6.) 

 Were we to imagine that a cluster of Grantia compressa had 

 grown so close as to press against each other, and the various 

 specimens to have coalesced into one mass, we would have a 

 correct idea of this variety. That it is, however, no variety of 

 Gr. compressa is proved by the difference of its texture, as well 

 as by the form of the spicula. 



7. G. CORIACEA, inci'usting ; texture cancellated, fihro- 

 Jleshy ; the sjncula minute, triradiate. 



Plate XXI. Fig. 9. 



Spongia coriacea. Montagu in Wern. Mem. ii. 1 IG. Gray, Brit. 



PI. i. 361. Flem. Brit. Anim. 526. 

 Grantia multicavata, Bean, MSS. 



Hah. On rocks between tide-marks. Scarborough, Mr Bean. 

 Berwick Bay, G. J. Dublin Bay, A. H. Hassall. 



Sponge incrusting, spreading irregularly, from one-eighth to 

 one-fourth ofan inch thick, dirty bluish gray or white when recent, 

 changing to yellowish-brown when dried or immersed in fresh- 

 water, of a fibro-cameous substance, soft and easily torn in any 

 direction, not elastic ; surface plain or uneven, cancellated, the 

 meshes or pores large, roundish, and separated by a thick line : 



