208 ANATOMY AND PHYSIOLOGY 



Suborder III. Solid, entirely spiculate, kerato-fibrous 

 skeletons. 



Chalina, Grant. 



Skeleton fibrous. Pibres keratose, solid, cylindrical, and 

 interspiculate. Rete symmetrical; primary lines ra- 

 diating from the basal or axial parts of the sponge to 

 the distal portions. Secondary lines of fibre at about 

 right angles to the primary ones. 



Type, Chalina oculata, Bowerbank. 



The type of this genus, Halichondria oculata, Johnston, 

 dififers so materially in the structure of its skeleton from 

 that of the type of Halichondria, H. panicea, Johnston, 

 that it becomes necessary that a distinct genus should be 

 established to receive it and other closely allied British 

 species. The skeleton consists of a solid, cylindrical, kera- 

 tose fibre, enclosing a single or compound series of spicula, 

 imbedded at or near its centre, and disposed in lines parallel 

 to its axis; thus forming a structural group intermediate 

 between that of Halichondria panicea and Spongia offi- 

 cinalis. 



In the sponges of this genus the spicula are decidedly 

 subservient to the fibre, which is always cylindrical, and 

 generally very uniform in its diameter throughout the whole 

 of a section made at right angles to its surface ; while in 

 the nearly allied genus, Isodictya, the reverse is the case, 

 the spicula being the essential basis of the skeleton, while 

 the surrounding keratode, although often abundant, is still 

 only the subservient cementing medium of the skeleton, 

 and never assumes the decidedly cylindrical form of that of 

 the fibre of Chalina. 



In the ' Edinburgh Encyclopaedia,' vol. xviii, p. 844, 

 Dr. Grant proposed the name Halina to represent those 

 species which were designated Halichondria by Dr. Fleming, 

 and subsequently by Dr. Johnston, in his ' History of 



