10 Mr. II. J. Carter on three Pachytragous Sponges 



minute stellates ; agglutinating to its surface minute rounded 

 grains of sand, amidst which are situated the exhalant aper- 

 tures (oscules) in the layer, without a raised margin, also the 

 inhalant apertures (pores), somewhat smaller, scattered gene- 

 rally throughout the exposed area; grains of sand (fig. 16 a) 

 blackened by a pigmental layer, which also lines all the cavi- 

 ties occupied by the sponge ; in direct contact with the body- 

 substance of the sponge internally. Body-substante (figs. 15 c, 

 IG (I) opalescent, soft, compact, composed of areolar sarcode 

 traversed in all directions by the branches of the excretory 

 canal-system, which, uniting, finally terminate in their respec- 

 tive oscules ; charged more or less with the same kind of stel- 

 lates as those in the dermal layer, together with minute sheaf- 

 like bundles of acerate spicules (figs. 20 «, 22), Avhich in certain 

 directions reflect the light like the micaceous particles in gra- 

 nite. Spicules of five kinds : — 1, the largest (fig. 17) smooth, 

 acerate, fusiform, slightly curved ; 2, smooth, trifid (figs. 18, 

 19), with shaft pointed at one end and provided with three arms 

 at the other, spreading horizontally in the opposite direction, 

 more or less inclined forwards towards the long axis of the 

 shaft, vase-like, straight or slightly flexuous, smooth, pointed ; 

 3, the same (fig. 19), with the ends of the arms more or less 

 bifurcated ; 4, stellate spicules, with large body (fig.21,rA) and 

 short thick rays, or with long rays and hardly any body {h) ; 

 5, sheaf-like bundles of minute, smooth, acerate spicules lying 

 parallel to each other (fig. 22). The large acerate spicules are 

 more or less spread throughout the sponge ; the trifid ones of 

 both kinds chiefly confined to the surface, where they are 

 arranged vertically witli their heads towards the dermal layer 

 and their shafts internally (fig. 16 c) ; the stellates, although 

 most numerous and packed together cnist-like in the dermal 

 layer, are also scattered throughout the body-substance ; while 

 the sheaf-like bundles of minute acerate spicules are entirely 

 confined to the latter. 



Size variable, depending chiefly upon the size of the exca- 

 vations, the largest of which are seldom more than half an 

 inch long and a quarter of an inch in diameter. Largest 

 acerate spicule a little less than l-20th of an inch long; longest 

 shaft of trifid spicules about l-30th inch ; stellates about 

 1 -2000th inch in diameter, and sheaf-like bundles of acerate 

 spicules about 1-lOOOth inch long. 



Loc. Budleigh-Salterton, south coast of Devon. Straight 

 Point. 



Hah. Cavities of the surface of sandstone rock made by 

 SaxicavcB and Annelids ; communicating with the exterior 

 through their openings, obscured by overgrowths of Cirripedes 



