56 PORIFERA. III. 



208 fathoms (The Fisher}' investigation steamer "Thor"). The localities are in the Den- 

 mark Strait. 



12. H. dubia n. sp. 

 PI. VI, Fig. 8. 



Incrusting; surface finely hispid. Spicula: megasclera ; the skeletal spicrdcs acanthostyli with a 

 small head, divided into tivo groups, large, only spined below, 0-34 o-j8'" m , small, entirely spined, 

 o-io o-2j""*; the dermal spicules strongyla 0-26 0-32"""; microsclera chela arcuata 0-040 0-057""". 



Of this species we have a specimen growing on a stone together with specimens of H. Koehleri, 

 baculifera Tops., curvichela, Eurypon sp. and Plocamia sp. The specimen has a greatest extent of only 

 io mra , and it is very thin. The colour (in spirit) is whitish. The surface is finely hispid. The dcrmai 

 membrane is thin, somewhat richly charged with chelae. Oscula and pores were not observed. 



The skeleton. The dermal skeleton consists of bundles of dermal spicules, stretching obliquely 

 from the skeleton below up to the surface; the bundles may vary with regard to the number of spi- 

 cules contained, but it is generally not great. The main skeleton is constructed in the typical way 

 and consists of erect acanthostyli with their heads based on the substratum, the longest of them reach 

 to the dermal membrane, and it would seem that they penetrate through it. Spongin seems to be 

 present at the base, but to a very slight degree. 



Spicula: a. Megasclera. i. The skeletal spicules are acanthostyli; they are divided into 

 two rather well separated groups; the larger styli are straight, or most frequently slightly curved, they 

 have a small head-swelling and they taper evenly out into a long apex; on the head-swelling there 

 are somewhat large spines, but for the rest the styli are nearly smooth, only on the lower part, near 

 the swelling, they are slightly gritty; the small styli are similarly shaped, but they are straight, the 

 shaft is totally spined, but the spines are sometimes somewhat dispersed. The length of the large 

 styli is 0-34 0-38 mm and the thickness at the base 0-035 mm ; t^ e length of the small styli is o-io 0-33' 

 with a thickness at the base of 0-02 0-028 mm , the greatest of these sizes, which form transitions to 

 the large styli, are of rare occurrence. 2. The dermal spicules are strongyla; they are straight and 

 cylindrical, not thicker in the middle; their shape is in so far characteristic as they grow evenly 

 thinner from one end to the other, so that one end is always distinctly thicker than the other. The 

 length is 0-26 0-32 mm , and the diameter in the middle about 0-005 nim . b. Microsclera are chelae 

 arcuatae; they have an evenly curved shaft, the alae are lobe-shaped, slightly triangular and the 

 tooth elliptical with a long, narrow tuberculum; generally the teeth have such a direction that they 

 lie in a straight line connecting the two ends of the chela; the most characteristic feature in the 

 chela is, that the shaft is flattened to a high degree and in such a way, that the front side is nearly 

 flat, the hinder side on the other hand somewhat rounded. The length of the chela is 0-040 o-o5i mm , 

 the thickness of the shaft is 0-003 mm and its breadth o-oii""". The chelae occur abundantly and some- 

 what close-lying in the dermal membrane. 



The species is related to H. Koehleri, but is distinguished by the large styli, which are nearly 

 smooth and by the strongyla being not polytylote; it is also related to H. nummulus, but from this 

 it is distinguished by the chelae with the flattened shaft and not recurved end-parts. 



