131 



PLATE LI. 



IsooifiTVA iNJiiSTiNCTA, Boioerba/iiJc. 



Vol. ii, p. 290, ' Mon. Brit. Spongiacte.' 



Fig. 1. — Represents a large s}Decimen from the 

 Diamond Grovmd, off Hastings. Natural size. It is 

 remarkable for tlie large size of the oscular orifices. 



Fig. 2. — Represents a specimen dredged off Guernsey 

 by Mr. ^Y. Saville Kent in 1870. Natural size. 



.Fig. 3. — A skeleton spiculum. X 250 linear. 



Fig. 4. — One of the tension spicula, from the inter- 

 stitial membranes. X 250 linear. 



I received five specimens in a bottle with spirit from 

 the Rev. Mr. Norman labelled, " Strang-ford Lough, 

 October 8th, 1869." Among them I found a specimen 

 of I. indistincta, of an ii'regidar massive form, nearly 

 one inch in leno-th and about eio-lit or nine lines in 

 diameter. It was solid in substance, but very soft and 

 compressible, and of a dark olive-gi'een colour. A few 

 small branches of a slender fucus were projected from 

 its surface, and it is j^robable that it was parasitical on 

 the ijlant in the living state. It agreed precisely in its 

 anatomical characters with the type-specimen. 



The specimen represented by fig. 2 is remarkable 

 from its great similitude in foiiii to Ophlitaspongia 

 papilla. It affords an admirable illustration of the 

 little dependence to be placed on form, size, and colour, 

 in discriminating the species of sponges. 



Mr. Peach has also found this species in Fowey 

 Harbour in 1847. 



ISOMCTYA SIMDLANS, BoilXivhank. 

 Vol. ii, p. 308, 'Mon. Brit. SpoiJgiadas.' 



Fig. 5. — A finely-developed specimen of the species, 

 from off Hastings. Natural size. 



