BRITISH SPONGIADiE. 51 



Genus, Pachymatisma, Bowerhank. 



1. Pachymatisma Johnstqnia, 5ower5«M^. 



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 ridges. 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 cylindjo-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 Halichondria 



