144 Mr. H. J. Carter on the Classification of the Spongida. 



one ; generally a simple acuate. Often accompanied by one or 

 more forms of flesh-spicule. Texture exceedingly and charac- 

 teristically dense in the axis and stem, diminishing in compact- 

 ness towards the surface, which, when hirsute, is, in the dried 

 state, often characterized by the presence of stiffened sarcode 

 matting together the long projecting spicules of the surface. 

 Forms massive and lobed, or digitate, branched, stipitate ; 

 branches uniting clathrously or continuously, so as respectively 

 to produce globular or compressed flabellate heads ; some- 

 times foliate and proliferous ; occasionally hollow, vasiform, 

 or tubular. 



Group 2. Plumohalichondrina. 



Here there are two forms of axial spicules, viz. : — 1, simple 

 acuate, smooth or spined ; 2, more or less pointed or inflated 

 at the ends, which are often microspined scantily or sparsely. 

 Echinating spicule club-shaped and spined. Flesh-spicule 

 for the most part that termed by Dr. Bowerbank " angulate 

 equianchorate " (that is, with bow-shaped shaft and aleeform 

 arms), sometimes accompanied by a bihamate orC-shaped flesh- 

 spicule, sometimes without any flesh-spicule at all. Forms 

 massive, lobo-branched ; branches compressed, dichotomous, 

 separate or anastomotic, flabellate proliferous. 



Group 3. Microcionina. 



Here the chief character is incrusting, spreading, extremely 

 thin, laminiform, hirsute. Spicules simple acuate (not fusi- 

 form) , with terminal subspherical inflation more or less spined 

 and fixed scopiformly in the cornified sarcode of the lamina, 

 mixed with or surrounded by smaller forms which are smooth. 

 Echinating spicule club-shaped and spined throughout. 

 Flesh-spicules, a minute navicular equianchorate and a tri- 

 curvate in variable quantities respectively. Forms incrusting, 

 thin, laminar. 



Group 4. Echinoclathrata. 



Structure massive, clathrate, reticulate, with echinated fibre. 

 Echinating spicule acuate, smooth or spined. Forms massive, 

 lobed. 



Group 5. Baculifera. 



Here the chief characters are the corky nature of the tissue 

 and the peculiar pin-like spicule, whose head is globular or 

 circular compressed, terminal, and applied to the shaft per- 

 pendicularly, so as, en profile, to resemble the head of a crutch. 

 But there being distinct fibre, and this being echinated as well 



