^Ir. II. J. Carter on the Genus Rossella. 115 



sponding witli tlie long transverse diameter of the body 

 (fig. 5, a), leading into a cavity of mucli tlie same shape as 

 that of the sponge externally (fig. 4, ee). Sessile or fixed by 

 anchoring-spicules. Colour grey. External surface uniformly 

 cribellate and monticular, covered by a thin layer of spicular 

 latticework, and surmounted by three forms of projecting 

 spicules situated respectively on the truncate end, on the body, 

 and on the conical end, as will be more particularly described 

 hereafter. Internal surface, or that of the cavity, uniformly 

 smootli, inteiTupted by depressions or pits increasing in size 

 towards the lower part. Body or wall constructed of a dense 

 interlacement of large and small spicules, rendered more solid 

 and areolar by the addition of sarcode charged with tlie minute 

 spicules of the species, and accompanied throughout by the 

 ramifications of the excretory canal-system. Layer of lattice- 

 work fomied of minute, sexradiate, spiniferous spicules, whose 

 horizontal arms, spreading out at right angles to and over- 

 lapping each other, form a quadrangular retiform structure 

 held together by the dermal sarcode. Pores situated in the 

 sarcode filling the quadrangular spaces of the latticework. 

 Vents opening into the pit-like depressions on the surface of 

 the cavity. Spicules of three kinds, viz. appendicular, struc- 

 tural, and flesh-spicules. A. Appendicular, of three forms, 

 corresponding with their respective localities : — 1. That con- 

 stituting an erect beard, about a quarter of an inch long, situ- 

 ated round the aperture (fig. 4, c), stout, linear, smooth, nearly 

 straight, fusiform, acerate, finely pointed at each end, averaging 

 10-12tlis by 8-1800ths of an inch in its greatest diameters. 

 2. Anchoring-spicule, which issues from the surface of the 

 body generally, beginning very scantily above in little groups 

 here and there, which increase in number, size, and length 

 towards the lower or conical end, where they attain their 

 maximum size and density (fig. 4,dd) : stout, smooth, linear, 

 commencing in a finely attenuated end which is fixed in the 

 sarcode of tlie body, and gradually passing into a thick shaft 

 which is abruptly terminated at the free end hj four opposite, 

 stout, recurved spines or hooks (fig. 3) ; average largest size 

 3 to 4 inches by 5-1800ths of an inch in its greatest diameters, 

 hooks 30 by 5-1800ths of an inch. 3. Crucially headed or 

 veil-spicules, projecting chiefly from the monticules, over every 

 part of the external surface but the aperture, consisting of a 

 shaft whose pointed or inner end is fixed in the sarcode of the 

 body, and whose free or outer one is terminated by four long 

 arms spread out horizontally so as to intercross with those of 

 its neighboiu-s, and thus form a general veil-like covering 

 separated from the body by the length of the shafts between 



8* 



