236 Miss Jane Stephens on 



(c) isochelse with a sliglitly curved shaft, 0*015-0024 mm. 

 in length. (3) Sigmata of two forms — (a) sigmata lying in 

 one plane and of very different sizes. The longer axis varies 

 from about 0* 1-0*4 mm. in length. The maximum thickness 

 of the spicule is 0*02 mm. ; [b) slender, contort sigmata with 

 a longer axis of 0'04-0*075 mm. 



Specimens of this species were obtained at two stations off 

 the south-west coast of Ireland at depths varying from 250 to 

 728 fathoms. 



lotrochota acanthostylifera, sp. n. 



The sponge is coating a piece of coral ; it is a good deal 

 injured. 



As far as can be seen, the main skeleton is an irregular 

 reticulation of acanthostyli. Here and there ill-defined fibres 

 are formed. The dermal skeleton consists of flat bundles of 

 spicules, or, in places, of longer fibres. 



Spicules. — (1) Acanthostyli, which are straight or slightly 

 curved. The head is a little swollen and is thickly set with 

 strong blunt spines. A few small spines are scattered along 

 the shaft. Length 0-32-0-35 mm. by O'OOS mm. (2) The 

 dermal spicules are tylota. The shaft is straight and the 

 ends are unequal, one end being more rounded than the 

 other. Length 0-3-0-33 mm. by 0005 mm. (3) Isan- 

 chora3, 0'045-0"5 mm. in length, with about 8-10 teeth at 

 either end. (4) Birotulse, 0'015 mm. in length. 



The species was dredged off the south-west coast of Ireland 

 at a depth of 627-728 fathoms. 



Hymedesmia helgce^ sp. n. 



The sponge is growing in a thin encrustation on coral and 

 on a piece of Ritepora. 



The main skeleton consists of acanthostyli, set vertically 

 with their heads on the substratum. The dermal skeleton is 

 made up of thick bundles of spicules, which are arranged 

 more or less vertically in the sponge. Beneath the surface 

 they spread out, and are continued as strong fibres running- 

 parallel to the surface of the sponge. The dermal membrane 

 is crowded with isochelae arcuatse. 



Spicules. — (1) The longer acanthostyli have a slightly 

 curved shaft and a head which is, at the most, very slightly 

 marked. The lower part of the shaft is thickly covered with 

 rather small spines; the remainder of the shaft is set with 

 very small spines, so small that the shaft looks merely 

 roughened. Length 0-25-0-35 mm. by 01 mm. The 



