64 BRITISH SPONGIAD^. 



distinctly to the eye. Delicately thin as this species 

 is, it is profusely aluindant in spicula. 



"At the first sight this sponge is liable to be mis- 

 taken for Hymedesmia indisUncta, but on a more care- 

 ful microscopical examination the difference in form of 

 the dermal tension spicula from those of H. indisUncta, 

 and the total absence of the entirely spined cylindrical 

 spicula of the last-named species, at once separates 

 them.'^ 



8. Hymedesmia Pbachii, Bow., n. sp., iv, PI, XIII, figs. 

 5—12. 



" Sponge coating exceedingly thin. Surface 

 smooth, or very minutely hispid. Oscula and pores 

 inconspicuous. Dermal membrane pellucid, aspicu- 

 lous. Skeleton composed of numerous very slender, 

 acuate spicula in flat fasciculi, irregularly dispersed ; 

 auxihary skeleton spicula large and long, attenuato- 

 acuate, basally spinous, irregularly dispersed, pros- 

 trate. Internal defensive spicula attenuato-acuate, 

 entirely spined, projected from the basal membrane at 

 right angles to its plane, comparatively small and 

 numerous. Retentive spicula large and very stout, 

 bidentate, equi-anchorate, moderately numerous ; and 

 rarely others of the same form exceedingly minute. 



" Colour. — In the dried state, cream- white. 



" Habitat. — Wick, North Britain, in deep water ; 

 0. W. Peach. 



" Examined. — In the dried state. 



" I received in 1866, from my old and indefatigable 

 friend Mr. 0. W. Peach, too late for description and 



