Dr. J. E. Gray on the Arrangement of Sponges. 287 



spicules scattered in the sarcode, which are generally of a small 

 size and uniform shape, and are characteristic of each suborder. 

 Thus they are hamate unilateral in the Hamispongia, sex- 

 radiate in the Sexradiatospongia, and stellate multiradiate, in 

 the form of spicular spherules, in the Quinqueradiate group. 



In the division of the marine sponges, like other natural 

 bodies, into suborders or types the characters of the orders 

 given are those of the general mass of species belonging to it ; 

 but there occur genera or families that have most of the 

 characters of the suborder or family but want the essential 

 character of the group — as the genus Sj^ongia^ which belongs 

 to the order Thalassospongia, but wants the characteristic 

 siliceous spicules. In the same manner Placospongia has the 

 spherical spicules of the quinqueradiate sponges, but appears to 

 be without the quinqueradiate spicules ; and the Chondrillad^e 

 have the many-rayed spicules of the same suborder, but also 

 want the five-rayed spicules — these groups being what Mr. 

 MacLeay called " aberrant types." 



Suborder I. Leiospongia. 



The sponges only strengthened by simple, elongate, sub- 

 cylindrical, fusiform spicules, tapering at each end, or enlarged, 

 club-shaped, or capitate at one or both ends. This suborder is 

 without spicules of the sexradiate or quinqueradiate types, or 

 the free spicules peculiar to each. 



This suborder contains many species, and requires much 

 study to make out its structure, which I am glad to say 

 Mr. Carter is bestowing upon it. 



It contains : — 



1. The Suherispongia, which are massive, with inosculating 



areolar cavities terminating in a vent on the surface— as 

 SuheritidcB and RaptMophoridce ('Annals,' I. c. p. 447). 



2. The Keratospongia, with a skeleton formed of reticulated 



horny fibres having one or more series of spicules in the 

 central line — as Chalinidce, Phakelliadce, HalichondriadcBf 

 and Polymastidce. 



3. The Ophistospongiaj with a skeleton like the Keratospongia, 



but with diverging spicules on its outer smi'ace — as 

 OpMstospongiadce ('Annals/ I, c. p. 447). 



Suborder II. Hamispongia (Ann. & Mag. Nat. Hist. 

 1872, ix. p. 448). 



Sponges with unilateral spicules, which are curved at each 

 end, and either subcylindrical or more or less expanded, in 



