219 



PLATE LXXV. 



IsoDiCTYA LAOiNiosA, BowerbcmJc. 



Fig. 1. — Eepreseuts tlie type-specimen half the 

 natural size. 



Fig. 2. — One of the slender, acuate, tension spicula 

 from the dermal membrane. X 250 linear. 



Fig. 3. — A retentive equi-anchorate spiculum from 

 the dermal membrane. X 1000 linear. 



Fig. 4. — A skeleton spiculum. x 250 linear. 



Fig. 5.— -An attenuato-acuate, incipiently, entirely- 

 epined, internal, defensive spiculum. X 250 linear. 



IsoDiCTYA LACiNiosA, BotverhcinJc. 

 Plate LXXV. 



Sponge sessile, fanshaped, thin. Surface uneven, 

 somewhat sinuous, laciniose, minutely hispid. Oscula 

 and pores inconspicuous. Dermal membrane pellucid, 

 si^iculous ; tension spicula acuate, long, and slender, 

 not very numerous ; retentive spicula dentato-palmate, 

 equi-anchorate, palm rather exceeding one third of the 

 length of the spiculum ; tooth terminally truncated, 

 numerous, very minute. Skeleton very diffuse and 

 open ; primary lines from three to five or six spicula 

 in thickness ; secondary lines irregular, mostly uni- 

 spiculous, occasionally containing two or three spicula. 

 Spicula acuate, stout, and large. Internal defensive 

 spicula attenuato-acuate, incipiently spinous, minute, 

 few in number. Interstitial membranes spiculous ; 

 tension and retentive spicula same as those of the 

 dermal membrane. 



Colour. — In the dried state, light brown. 



