66 PORIFERA. III. 



20. H. longistylus n. sp. 

 PL VII, Fig. 7. 



Intrusting; surface somewhat hispid. Spicula: megasclera; the skeletal spicules acanthostyli rvith 

 the base thickened, but not forming a real head, the longer only spined at the base, the smaller in the 

 zvhole length, o-io o-^2 mm , not divided into two groups; the dermal spicules subtornota to tornostrongyla 

 0-238 028""*; microsclera chela arcuatce 0-025 0-045""". 



Of this species one specimen grows incrusting on a Retepora ; it grows in several places on 

 both sides of the Retepora and through the holes of this, so that by looking through the holes the 

 projecting spicules of the sponge are seen bordering the holes; another specimen grows on a stone. 

 Its greatest extent is 14 mm , and the thickness does not go beyond 0-5 mm . The colour (in spirit) is 

 greyish white or white. The surface is in the present state of the sponge strongly hispid from the long 

 projecting spicnles, but the dermal membrane is in most places damaged; only in some single places 

 it is seen; it is a thin film, which seems to be in a somewhat loose connection with the other body; 

 the membrane is provided with scattered dermal spicules. In the places where the membrane is 

 present, the sponge seems to be somewhat hispid, the longest skeletal spicules being somewhat 

 projecting. 



The skeleton. The dermal skeleton consists of loose fibres and scattered spicules which are 

 placed between the longest of the skeletal spicules; in the membrane itself there are found horizontal, 

 scattered spicules. The fibres or bundles may in places be somewhat thick. The main skeleton is 

 formed in the ordinary way of vertical acanthostyli; the longest of them project beyond the surface, 

 thus making the sponge strongly, but somewhat dispersedly hispid; the styli are not placed densely. 

 There seems to be some spongin at the base, but I could not observe it with certainty. 



Spicula: a. Megasclera. i. The skeletal spicules are acanthostyli; the longest are slightly 

 curved, the small are straight. In the large styli the head end is thickened, but a real head is not 

 marked off, in the small styli the head is more distinctly marked; the styli taper into a long, fine 

 apex; the largest ones are only spined at the base, the small in the whole length, and the spines are 

 relatively largest in the small styli. The length varies exceedingly, but all intermediate sizes are 

 found, the smallest are present in greatest numbers. The length is o-io 0-92 mni and the diameter of 

 the head 0-014 o-o28 nim . 2. The dermal spicules may best be termed tornota, the ends may be 

 slightly swollen, most frequently this is only the case with one end which then has a distinct, short 

 point, while the other end sometimes is somewhat rounded, so that the spicule might be termed a 

 tornostrongyle; the spicules are straight and not thickened in the middle. The length is 0-238 o - 28 ram 

 and the diameter 0-0028 0-005 """ b. Microsclera; these are chelae arcuatse, they are of common 

 shape with an elliptical tooth and lobe-shaped alse; the shaft is evenly curved and somewhat flattened. 

 The length is 0-025 0-045 mm an ^ the diameter of the shaft 0-0028 0-007 mm in relation to the size and 

 to whether the chela is seen in side or in front view. The chelae are found scattered in the tissue, 

 but not, or only singly, in the dermal membrane. 



This species shows some resemblance to H. perforata and curvichda, but perforata has shorter 

 styli and pure tornota, and also the main skeleton is much more dense; citrmchcla has similar styli, 



