174 BRITISH SPONGES: 



whiter colour ; but, as in other spoiig-es, the external surface is 

 always of a closer texture than the inner. 



The Grantiaa are properly littoral, growing on, or hanging 

 from, rocks, sea-weeds, shell-fish and corallines, between tide 

 marks, or in shallow water within the lowest ebb. In conse- 

 quence of this their position, the circulation of water through 

 their body has periodical interruptions, and it is said to be more 

 languid than in some siliceous sponges inhabiting similar loca- 

 lities. Of its reality, Dr Grant's authority leaves no doubt, 

 but its existence is less easily demonstrable than has been as- 

 serted. I have in vain made repeated experiments at all sea- 

 sons to see it. I have been equally unsuccessful in discovering 

 anything like ova or gemmules in this genus ; nor is there any 

 difference in the structure and composition of the sponge at any 

 period of growth that is appreciable. 



* Tubular. 



1. G. COMPRESS A, compressed^ leaf-like^ with terminal 

 and lateral orifices ; surface even and porous ; the spicula 

 triradiate and clavate. 



Plate XX. Pig. 1. 



Spongia compressa, Fabric. Faun. Groenl. 448. Turt. Gmel. iv. 

 661. Sosc, Vers, ill. 176. Jameson in Wern. Mem. i. 562. 

 Lamour. Cor. Flex. 48. Corall. 168. Grant in Edin. New 

 Phil. Joiirn. i. 166 ; and ii. 122, 127, pi. ii. fig. 11, 12, 13, and 

 23 ; copied in Blainv. Atlas, pi. 94. 



Spongia foliacea, Montagu in Wern. Mem. ii. 92, pi. 12. Temple- 

 ton in Mag. Nat. Hist. ix. 471. 



Scypha foliacea, Gray, Brit. PI. i. 358. 



Grantia compressa, Flem. Br. Anim. 524. Johnston in Trans. 

 Newc. Soc. ii. 270. Bellamy's South Devon, 268. Hassall in 

 Ann. Nat. Hist. m'\. 174. 



Leuconia compressa, Grant's Out. Comp. Anat. p. 7, fig. 3. 



La Calceponge comprimee, Blainv. Actinol. 531 . 



