488 PROF. P. M. DUNCAN ON THE GENUS DIRRHOPALUM. 



Part II. 



Descriptions of two additional new Species of Dirrhopalum. 

 By Prof. P. Martin Duncan. 



During an examination of some debris which had been brought 

 up by the dredge and tangles from the North Atlantic by 

 H.M.S. ' Porcupine,' and from off the south-west coast of Spain 

 in association with corals, I found an Echinus -spine, and also a 

 darkly stained calice of a coral. Both were more or less covered 

 with bristly sponges of an incrusting habit, and with very remark- 

 ably shaped, bent, cylindrical, terminally-inflated spicula forming 

 the basis. A careful examination proved that they must be 

 associated with Oscar Schmidt's genus Plocamia. 



The first species to be described came up with a mass of the 

 coral Amphihelia ramea, Sars, from the Globigerina-ooze in deep 

 water from the North Atlantic ; it covered an Echinus-spine. 



The spine (PL XXIX. fig. 18), about two thirds of an inch 

 in length, has been fractured ; but what remains is covered with 

 a very delicate incrustation of a very spiculiferous siliceous 

 sponge. This is silvery white in colour, and shows neither 

 oscules nor pores ; but a considerable number of regular minute 

 elevations are visible, out of the centre of each of which projects 

 a large glassy spiculum. A low magnifying -power shows that the 

 elevations are produced by whorls of spicula which radiate nearly 

 at right angles from one spot around each large glassy spicule. 

 The blunt ends of the radiating spicula are towards and in con- 

 tact with the axial spicule ; and their sharp terminations describe 

 a circle, the periphery of which touches those of the neighbour- 

 ing whorls around other large spicula. 



The whorls have the spicula close together near the great or 

 axial spicula, but they permit the sharp distal ends to be slightly 

 separated. A sarcode fills up and covers all (PI. XXIX. 

 figs. 18 & 30). 



Underneath this layer of whorled spicula there is a close 

 layer of curved, cylindrical, globose-headed, entirely-spined spi- 

 cula, which rests on the Echinus-spine. The large glassy axial 

 spicula start from this layer and project at right angles to it 

 (PI. XXIX. fig. 30). 



There are several kinds of spicula, which may be considered 

 under the heads of those of the outer skeleton, the body, and the 

 derm. 



