ADDITIONS. 359 



of the large acuate form that I described in the struc- 

 ture of the sponge, Vol. II, page 277, in treating of the 

 skeleton spicula, as " small and slender, numerous, and 

 the same form, large and long." They are irregularly 

 disposed and among them there are a few bihamate 

 retentive spicula, none of which were observed in the 

 examination of the small fragments of the dermal mem- 

 brane of the type- specimen. A few of the smaller 

 descriptions of acuate spicula were intermixed with the 

 larger forms in the dermal membrane, and on the 

 interstitial membranes the small slender ones were 

 very much more abundant than on the same tissues in 

 the Bantry Bay ones. The great difference in the size 

 of the tension spicula in the two forms of membrane is 

 an unusual circumstance, and it thus becomes an 

 important specific character in the discrimination of 

 the species. The dermal membrane is rather thick, 

 and in the dried state it is of a light fawn-yellow 

 colour, and from its general appearance it is very 

 probable that in the living state the surface would be 

 smooth and even. Under these circumstances the 

 following should be substituted for the specific 

 character in page 277, of the present volume. 



CHALINA INOENATA, Bowerbank. 



Sponge, massive, sessile. Surface smooth and even. 

 Oscula simple, dispersed. Pores inconspicuous. Dermal 

 membrane, stout, abundantly spiculous ; spicula acuate, 

 large, irregularly dispersed, and a few of the same 

 form small and slender, retentive spicula; bihamate, 

 simple and contort, few in number. Skeleton. Rete 

 rather coarse and open, irregular, abundantly spiculous ; 

 spicula subfusiformi-acuate, very rarely acerate, small 

 and slender, numerous ; and the same form large and 

 long as in the dermis, few in number near the circum- 

 ference of the fibre. Interstitial membranes, abun- 

 dantly spiculous, spicula small and slender. 



