290 Dr. J. E. Gray un the Arrangement of Sponges. 



the shaft, and the lower end is generally much elongated ; and 

 for this reason they have been called four-rayed, trifurcate, or 

 nail-like spicules. They frequently have free, but more or 

 less abundant, regular-shaped many-rayed spicules, or spicular 

 spherules, scattered in their flesh, which are always of a small 

 size, and more or less regular in their shape. 



This order consists of the Sphgerospongia and the family 

 MacAndi-ewiadse of the 'Annals,' 1872, ix. p. 456. 



Section I. Five-rayed or skeleton-spicules often united by 

 siliceous matter ; flesh-spicules fusiform, cylindrical, 

 more or less spinose. Lithistidce ^ Carter (Ann. & Mag. 

 Nat. Hist. 1873, xii. p. 437) ; MacAndreiviadce, Gray 

 (Ann. & Mag. Nat. Hist. 1872, ix. p. 456. 



The sponge formed of superficial sexradiate spicules, which 

 are held together by an amorphous siliceous coat. 



Mr. Carter gives an arrangement of the species of the 

 various genera of this group, to Avhich the genera Mac- 

 Andrewia and Theonella^ Gray, CoralUstes and Leiodermhtium 

 of Schmidt, and Azorica and Lithospongitis, Carter, are re- 

 ferable. In the 'Annals' I placed MacAndrewiada3 with the 

 Coralloid sponges having sexradiate spicules ; but the ex- 

 amination of more spicules has proved that they belong to the 

 quinqueradiate type, with the habit of the coral-sponges. 



Section II. The skeleton-spicules elongate, free from one 

 another, generally forming the circumference of the 

 sponge, sometimes projecting beyond it. 



a. The free flesh-spicules many-rayed, stellate, on the outer 



surface or inner part of the sarcode. Tethyadce^ Dona- 

 tiadcB^ The7ieadce^ Lophurelladce^Casuladce. [See Ecio- 

 nemia acervus^ and E. densa, Bowerbank, Proc. Zool. 

 Soc. 1873, t. XXX. figs. 1-14.) 



b. With spicular spherules forming the outer surface of the 



sponge. Geodiadce. 



c. The spicular spherules crowded together, and forming 



the axis and plates on the outer surface of the coral- 

 like sponge, with the sarcode and spicules between the 

 two. Placospotigiadcv. 



d. Without any many-rayed stellate spicules or spicular 



spherules. Ancorinadce. 



e. Aberrant family, Chondnlladce, with many-rayed stellate 



flesh-spicules, but without any elongate five-rayed 

 spicules. See Chondrilla australiensis, Ann. & Mag. 

 Nat. Hist. 1873, xii. pi. 1. figs. 14-16. 



