BRITISH SPONGIADiE. 51 



Genus, Pachymatisma, Bowerbank. 



1. Pachymatisma Johnstonia, Bowerbank. 



Halichondeia Johnstonia. Trans. Mic. Soc. London, vol. i, p. 63, 



pi. vi. 

 Johnston. Hist. Brit. Sponges, p. 198. 



Sponge. Massive, sessile ; surface smooth, undulating 

 into riclges. Oscula simple, congregated on the ele- 

 vations. Pores inconspicuous. Dermis crustular, 

 filled with ovaria : dermal membrane pellucid, abun- 

 dantly spiculous ; spicula fusiformi-cylindrical, tuber- 

 culated, minute. Intermarginal cavities immersed in 

 the dermal crust, separate, symmetrical, sub-cylin- 

 drical, valvular at proximal end. Connecting spicula, 

 attenuate or cylindro-patento-ternate, radii variable in 

 form and proportions. Skeleton, spicula cylindrical, 

 variable in form and proportions. Spicula of sarcode 

 attenuato-stellate, radii incipiently spinous, rarely fully 

 spinous, or obtuse. Ovaria oval, depressed. 



Colour. Littoral specimens, light to dark slate gray. 

 Deep sea specimens, pink or red. Capt. F. W. L. 

 Thomas, R.N. 



Habitat. Rocks between high and low water mark, 

 Torquay, Guliot Caves, South Coast of Ireland, Bower- 

 bank ; Orkney Islands, 35 fathoms, Capt. E. W. L. 

 Thomas, R.N. ; Wick, Scotland, C. W. Peach. 



Examined. In the live state. 



I described this sponge in a paper read before the 

 Microscopical Society of London, November 24, 1841, from 

 specimens which I found attached to the rocks between 

 high and low water marks, and designated it Ilalichondria 



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