. REPORT ON THE HEXACTINELLIDA. 245 



Finally, the pleuralia include isolated two-toothed, very rarely threc-tootlied, anclior 

 forms with a strong shaft bearing barbs. These occur more abundantly towards 

 the base, and seem to be wholly absent from the upper end of the sponge-body. The 

 inner portion of these spicules, which vary greatly in length, is smooth, and ends in a 

 simple uniform point. On the outer j)ortion inconspicuous tubercles first appear, these 

 are succeeded by larger forms, which finally pass into strongly developed spines pointed 

 backwards and slightly recurved. In the portion of the anchor shaft which is surrounded 

 by barbs the diameter of the spicule rod decreases gradually outwards. Just in front of 

 the end which bears two simple anchor teeth the barbs disappear, and the diameter 

 again increases on to the thickened end with its slightly arched apex. From the latter 

 the two strong roundish (about 1 mm. in length) anchor-teeth originate laterally in a 

 distal plane. They extend opposite one another — smooth and slightly curved — and are 

 directed obliquely outwards and backwards. In abnormal cases three similar anchor 

 teeth occur, forming equal angles with one another, or the number may be reduced 

 to one. 



The basalia forming the numerous slender tufts' — about 2 mm. in thickness — which 

 project from the lower rounded end of the sponge, are for the most part of great length, 

 and may in the larger specimens, as Wyville Thomson has shown, measure several 

 decimetres. They are, on the whole, stronger than the pleuralia, and form in spirit or 

 dried specimens a thick feltwork, between the fibres of which, portions of the substratum 

 and all kinds of foreign bodies are included (PI. XLIII. fig. 1). In their upper portions 

 all the fibres are smooth, while externally they exhibit, for the most part, perhaps with- 

 out exception, the curved barbs described above in connection with the shaft of the 

 pleural anchors. Like the pleural anchors, further, they pass by a smooth cyKndrical 

 neck to a thickened terminal portion with two more or less large recurved anchor teeth. 



The marginalia surrounding the circular margin of the oscular aperture form a 

 closed wreath — a few spicules in breadth — and consisting either of long, strongly 

 developed uncinates like those which occurred among the pleuralia, or of perfectly 

 smooth, internally pointed, externally narrowed spicules of various calibre, which 

 probably end in a point or in a spinose portion with terminal knob. 



"While on the internal surface of the gastral cavity of the Hyalonematids no spicules 

 projected except the pinules, in this form numerous uncinates occur in the neighbourhood 

 of the marginal fringe, arranged in tufts directed inwards and upwards, and projecting 

 freely for about half theii- entire length into the lumen of the gastral cavity (PI. XLIII. 

 fig. 2). 



' Oscar Schmidt has, in his Spongien ties Meerbuseiis von Mexico (p. 65), maintained that the Pheronema figured by 

 Saville Kent (Monthly Micr. Journ., 1870, pi. Ixiii. fig. 1) is not AVyrille Thomson's Pheronema carpenteri, hut 

 Pheronema annse, Leidy. With this opinion I cannot agree. The hasalia do indeed protrude as in Plieronema annse, 

 but the same occurs in Pheronema carpenteri, though to a less marked degree. Besides, as Saville Kent notes, the 

 specimen was much macerated, so that the individual Imndles of basalia were naturally isolated. 



