286 A MONOGRAPH OF THE 



were acerate in form, and were of an average length 

 of ^th inch ; they were very numerous, closely packed, 

 and radiating in the direction of lines drawn from the 

 centre to the circumference of the gemmules. It is pro- 

 bable that the acerate form may not be that of the spicula 

 of the adult gemmules, as we find in those of Geodia and 

 Pachymatisma, that the radiating spicula of the gemmules 

 are acerate in the imperfectly developed state, while in the 

 fully developed condition the outer points are replaced by 

 planes which form the bases of a series of elongated conical 

 spicula, the united apices of which form the inner surface 

 of the gemmule, while the united bases form a firm and 

 even outer surface to that organ. When digested in boiling 

 nitric acid, the gemmules entirely disappeared, and I could 

 not find a single detached spiculum belonging to them ; 

 this result renders it the more probable that they were in 

 an early and imperfect stage of development. 



A full-sized skeleton spiculum measured -^th inch in 

 length. I have named this species in honour of my friend 

 Mr. McAndrew, who has done so much to advance our 

 knowledge of marine natural historv, and to whom I am 

 indebted for my knowledge of this and many other species 

 of British and exotic sponges. 



9. ISODICTYA INDEFINITA, Bowefbcillk. 



Sponge. Massive, sessile; surface uneven (?). Oscula 

 simple, dispersed (?). Pores unknown. Dermal 

 membranes aspiculous (?). Skeleton. Primary lines 

 multispiculous ; secondary lines unispiculous ; rete 

 the width of the length of the single spiculum ; 

 spicula acerate, stout. Interstitial membranes ; ten- 

 sion spicula acerate, slender. 



Colour. Alive, scarlet. Dried, light brown. 

 Habitat. Ilfracomb, Mrs. Griffith. 

 Examined. In the dried state. 



