sPOBrarDDA. 609 



30. Desmacidon rimosa *. (Plate LIII. fig. F ; Plate iAY. 

 figs, m-m".) 



Erect, stipitate ; stem and branches solid, more or less antero- 

 posteriorly compressed, except the extreme apices of the latter, which 

 are cylindrical and terminally rounded, finger-like. Branching 

 very irregular, not confined to one plane, the first division approxi- 

 mately dichotomous; the resulting (secondary) axes are eith,er 

 flattened strongly (2-4 times as broad as they are long), with but 

 short suboylindrical marginal branchlets,.or subcylindrical, giving 

 off several subcylindrical (tertiary) branches ; the largest of these 

 branches may attain a length of 35 mUlim. ; diameter of tips 

 of branches, just before termination, 4-5 milUm. Surface of stem 

 and, to a less extent, of branches scored by winding furrows, 1-3 

 miUim. deep, 1-3 miUim, wide, generally directed transversely when 

 on the flat surface of the branch, more longitudinally when they 

 have reached its margin ; they either vanish by becoming gradually 

 shallower distaUy, or end abruptly in an oscular opening. ' Vents 

 •5 to 1-5 miUim. in diameter, circular, deep, numerous, scattered 

 along the above-mentioned grooves. Surface pilose, like coarse 

 velvet, owing to projection of primary skeleton-fibres to a height of 

 ■25 to 1 mUlim., at distances of "25 to Imillim. apart. Texture 

 in spirit firm, tough, subelastio, the surface slightly harsh to the 

 touch; colour in spirit normally brown, inclining to grey, and 

 to rufous where skrinkage or abrasion of saroode has more or less 

 exposed the skeleton. 



Main skeleton^primary fibres vertical to surface, about -07 

 miUim. thick, •28-'35 mUlim. apart ; the secondaries vertical to the 

 primaries, about -05 mUlim. thick, •28-'35 millim.' apart : fibres 

 cored by spicule no. 2, with a few of no. 1 near the centre of the 

 sponge ; the horny fibre is ' almost wholly obscured by spicules ; 

 near the surface a distinct clear pale brown transparent margin 

 of about a quarter the thickness of the fibre is usually left. 

 Dermal skeleton made up of triangular to polygonal meshes (■28-'8 

 milUm. wide) 'of spiculo-fibre, •035-"09 millim. thick, strength- 

 ened by much pale brown transparent horny substance, which is 

 seen outside the spicules in the narrower fibres ; the contained spi- 

 cules are chiefly no. 1 ; the stouter fibres contain also, superficially, 

 no. 2. Sarcode transparent, pale yellowish brown. 



Spicules of skeleton: — (1) Acuate, smooth, slightly curved, tapering 

 gradually, more rapidly towards apex, to moderately sharp point, and 

 diminishing slightly in diameter towards the rounded base ; length 

 about "35 millim. ; diameter, base '019, middle of shaft -022 millim. 

 (most abundant in the fibre near surface, occasionally free in saroode). 

 (2) Acuate, approximately straight, tapering gradually from near 

 head to sharp point ; the base occasionally provided with a small 

 number of minute spines; size •23-*33 by •005--01 millim. (some- 

 times loose in sarcode, especially in dermis). 



* Bimosus, full of furrows, referring to the appearance of the surface. 



2b 



