178 Mr. H. J. Carter on the 



In the Amorphosa the acerates are for the most part long and 

 fine-pointed. 



In the lsodictyosa the acerate spicules are for the most part 

 short and more or less attenuated towards the points ; arranged 

 " net-like, " isodictyal." 



In the Thalyosa the spicules are much the same in size and 

 shape as in the foregoing family, but the specimens for the most 

 part branched and large ; the branches solid and subcylin- 

 drical, also white like chalk when dry. Very subject to a 

 parasitic polype sunk into the surface. 



In the Crassa the spicules are robust, and the specimens 

 chiefly large and massive. Forms often excavated cup-like or 

 crateriform. 



Group 5. Fibulifera. 



Sarcode colourless. Skeleton composed of fine spiculo-fibre 

 whose interstices are filled by an areolar sarcode like crumb 

 of bread. Surface uniform, openly reticulate, cancellous, or 

 covered with a fine network. Colour pale tawny, white, or 

 brown. Vents distinct and scattered, on a level with the 

 surface when external ; and when excavated, on a level with 

 the internal surface or that of the excavation. Pores in the sar- 

 code which tympanizes the interstices of the dermal reticulation. 

 Texture open, delicate. Spicules of two kinds, viz. skeleton- 

 and flesh-spicules : skeleton-spicule of one form only, viz. 

 simple acerate, more or less attenuately pointed ; flesh-spicule 

 also of one form only, viz. simple C-shaped or bihamate 

 ("fibula," Sdt.). Forms incrusting, parasitic, or massive and 

 lobed ; or cylindrical, branched, solid ; or funnel-shaped and 

 excavated. Much subject to a parasitic polype sunk into the 

 surface. 



Group 6. Halichondrina. 



Sarcode pale tawny or brown-purple. Skeleton composed 

 of reticulate spiculo-fibre whose interstices are filled up by 

 an areolar sarcode which, when dry, resembles crumb of bread. 

 Surface uneven, cancellated, reticular, rough. Colour tawny, 

 ochre-yellow, or brown-purple. Vents distinct, scattered, on 

 a level with the surface or on the prominent parts of mammi- 

 ferous lobes. Pores in the dermal sarcode which tympanizes 

 the interstices of the cancellated surface. Texture crumb-of- 

 bread-like, soft, crushable. Spicules of two kinds, viz. skele- 

 ton- and flesh-spicules. Skeleton-spicule for the most part of 

 two forms, viz. : — 1, simple acuate, smooth or more or less 

 spined ; 2, acerate, curved, fusiform, smooth ; or subcylindrical, 

 substraight, or subfusiform ; terminated by more or less inflated 



