18G7.] DR. J. E. GRAvr ON SPONGES. 497 



Dr. Oscar Sclimidfc gives the following syuopLlc:il table of liis 

 genera of Ceraosponguv : — 



I. With only one kind of elongated, homogeneous, horny filaments. 



Filament very elastic, difficult to split, and very 



variable in thickness Spongia. 



Filament slightly elastic, of unequal thickness .... Cacospongia. 



Filament scarcely at all elastic, extremely brittle when 



dry , Spongelia. 



11. With only one kind of elongated, non-homogeneous filaments. 

 The bark and axial substance of the filaments different Aplysina. 



III. With two kinds of horny filaments. 



The second kind forming a superficial network .... Ditella. 

 The second kind terminating in a little head. 



Tissue of the finer filaments loose Hercinia. 



Tissue of the finer filaments dense Saiicotragus. 



The Halichondrice he divides into genera thus : — 



I. The firm horny substance evident, surroundin(/ the spicules. 



The whole sponge-body uniform, horny, and spicular. 



Branches numerous, anastomosing Clatiiria. 



Branches slender, not anastomosing Raspalia. 



Part of the sponge horny and part crustaceous. 

 Sponge crustaceous ; the horny substance forming 



irregular processes Scopalina. 



Sponge branching ; the horny substance only in 



the axis Axinella. 



II. The horny substance none, or little evident. 



The inhaling-pores in sieve-like groups (^ribrella. 



The inhaling-pores scattered. 



Oscules on peculiar papilla Papii.lina. 



Oscules various. 



Skin-clothing very obvious, and alone pigmented . . Acanthelia. 



Skin-clothing when present without pigment, or 

 with the parenchyma alone pigmented. 



Spicules or needles blunt at the end, and generally 



knobbed, with special hook-shaped corpuscles . . Esperia. 



Spicules or needles blunt at the end, and generally 



knobbed, without hook-shaped corpuscles Suberites. 



Spicules or needles very simple, generally with both 



ends pointed Renieri. 



Spicules or needles smooth and nodose, mucous, ge- 

 latinous ]\Iy.\'illa. 



Boring into limestone or shell Vioa. 



Proc. Zool. Soc — 1807, No. XXXII, 



