184 Mr. H. J. Carter on the 



more or less tough within when fresh, but light, cellular, and 

 crumb-of-bread-like when dry. Spicules of two kinds, viz. 

 skeleton- and flesh-spicules, — the latter noticed in the descrip- 

 tion of the cortex, and the former in that of the " zone " and 

 the "body-substance" respectively. Forms mentioned at the 

 commencement. 



Group 15. Stellettina. 



The same, but with no " globular siliceous bodies " on the 

 surface, and therefore no stony cortex, but with a thick dermal 

 layer composed of long fusiform contractile (muscular ?) cells ; 

 charged with stellates and the flesh-spicules of the species. 



Group 16. Tethyina. 



Hemispherical or globular, fixed by an extended or con- 

 tracted base ; or globular and free ; or ellipsoidal and fixed, 

 root-like, by tufts of long anchoring-spicules. Surface hirsute 

 from the ends of the spicules, which project through the dermal 

 layer to a greater or less extent, arranged in separate tufts ; or 

 reticulately or in lines tending in a spiral direction towards 

 the summit. Dermal layer thick and tough, with or without 

 the flesh-spicule. Internal structure radiate ; radii composed 

 of bundles of spicules, which extend from a nucleated centre 

 towards the circumference through a compact areolar sarcode, 

 and in a more or less gyrate course from the base to the sum- 

 mit. Colour grey or brown externally, bright yellow when 

 fresh within or purple throughout, especially on the surface. 

 Vents apical, or scattered over the surface singly or in groups. 

 Pores in the interstices of the hirsute dermal reticulation. 

 Excretory canal-system not well pronounced, probably owing 

 to the compact and contractile nature of the areolar sarcode of 

 the body. Texture tough, hard, and compact throughout, 

 especially in the dermal layer. Spicules of two kinds, viz. 

 skeleton- and flesh-spicules. Skeleton-spicule of two forms, 

 viz. : — 1, large, acerate, more or less curved ; 2, anchoring- 

 spicule — that is, spicules composed of a long delicate shaft with 

 three arms of equal length extended fork-like in some, and 

 recurved anchor-like in others, like the " anchoring-spicule " 

 of the foregoing families ; arms sometimes unequal in length 

 in the fork-like heads, one being much longer than the other 

 two, which are equal. Sometimes the arms of the fork-like 

 form are much expanded, and the shaft of the spicule enlarged 

 altogether, so as to somewdiat resemble the " zone-spicule " of 

 the Geodina. Flesh-spicule of one kind only, viz. bihamate 

 or C-shaped contort (». e. spiral), for the most part minute and 



