SPONGES COLLECTED IN POKTO RICO. 
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Skeleton . — Strong spiculo-fibers about 0.5 mm. thick course, at oblique angles to vertical axis of 
body, through interior; breaking up 5 mm. or thereabouts from surface into smaller bundles, which 
radiate out to the surface. These fibers cross frequently, fusing at the points of intersection, and thus 
give rise to scattered, sometimes star-like, centers, from which the fibers seem to radiate. The outer 
smaller radiating bundles frequently (always?) arise from peripherally situated nodal points of this 
sort. Abundant scattered spicules lie between the fibers and peripheral bundles. At the surface are 
closely set diverging bundles of small strongyloxeas. 
Megascleres. (1) Chief spicule is a smooth fusiform strongyloxea, 1.5 mm. by 40 p or thereabouts; 
strongylate end greatly narrowed. Smaller stages in development of the same spicule are found. 
Occasionally oxeate end is rounded, spicule becoming nearly isoactinate. (2) Strongyloxeas of about 
same size as (1), not fusiform; with basal end rounded but not narrowed, and with tapering end also 
rounded at apex; not common. Both (1) and (2) make up the fibers and peripheral bundles, and 
are also found scattered. (3) Small strongyloxeas, frequently about 300 by 7 n, with basal end rounded 
not narrowed, make up the surface brushes; also scattered in interior, together with smaller slenderer 
forms, probably stages in development of same spicule. 
Suborder II. HAUCHONDRINA Ridley & Dendy. 
Typically noncorticate; skeleton usually reticulate; megascleres usually either oxeas or styles. 
Family HOMORRHAPHID/E Ridley & Dendy. 
Megascleres all diaetinal, either oxeas or strongyles; no microscleres. 
Subfamily RENIERIN^E Ridley & Dendy. 
The spicules may be united together by a small proportion of spongin, but are never completely 
enveloped in it. 
Genus PETROSIA Vosmaer (1885). 
Sponge usually hard; skeleton more or less confused; spicules oxeate to strongylate, packed 
together in tracts. 
Petrosia halichondrioides, n. sp. 
Station 6079, one specimen. 
Sponge a cake-shaped fragment, about 50 mm. diameter, with a thickness of 15 mm. ; outer surface 
convex and bearing one small excentrically placed osculum 3 by 1.5 mm. Surface even and slightly 
pilose. Consistency very dense and firm, though not hard; sponge becoming hard and brittle on 
drying. Color: Exterior, chocolate-brown; interior, somewhat lighter. 
Canal system of such a character that the sponge body is divided into trabeculae of a more or less 
uniform width (commonly about 60 p ) , the canals between being as wide or wider than the trabeculae. 
In the superficial region, the trabeculae and intervening canals in some places, but not universally, 
run more or less vertically to the surface; in the interior, they pursue a meandering course. Spicules 
in the trabeculae form tracts (scarcely bundles), which are vaguely defined, because the spicules are 
so loosely packed, without perceptible spongin. The tracts vary in thickness and distinctness, the 
larger ones sometimes running more or less vertically to the surface, again pursuing a tangential 
course. Following the anastomoses of the meandering trabeculae, the tracts of spicules form a quite 
irregular and vaguely defined reticulum. The tracts of spicules in the trabeculae of the superficial 
region pass, often very obliquely, into vaguely defined brushes of spicules which project radially from 
the surface. 
Dermal membrane indistinctly differentiated from subjacent tissue, perforated by numerous, 
diffusely scattered, rounded pores about 40 /t in diameter. The spicules lying between the pores give 
rise to a loose reticulum. These spicules are merely the outermost layer of the main skeleton. 
Spicules are slender for a Petrosia. Oxea 160 p by 4 to 5 p, smooth and slightly curved; very 
commonly somewhat irregularly bent in the middle, or sometimes with a slight prominence at that 
point. 
