340 THE VOYAGE OF H.M.S. CHALLENGER. 



on PI. XOVIII. fig. 3. Moreover, the results of microscopic examination of the beams of 

 the framework are in complete accordance with the description by Marshall and ]\Iurie. 

 All the beams of the network, the meshes of which are not always quite regular, though 

 generally square, are more or less richly beset with prongs which are either low and 

 pointed, or larger, broader, and more acute, as shown in PL XCVIII. fig. 11. The whole 

 framework is traversed by round canals, from 2 to 3 mm. in width, which open out 

 laterally. 



In the comparatively well-preserved large specimen studied by Murie, whose original 

 figure I have copied on PI. XCVIII. figs. 1, 2, and 4, ring-like or spiral wreaths were 

 found to originate laterally on the branches of the stock, while between these bands 

 of approximately uniform breadth occur. It is only in these wreaths that the ex- 

 tremities of the laterally bent longitudinal fibres of the dictyonal framework project 

 freely (PL XCVIII. figs. 2, 4). Although, moreover, in the case of the specimen examined 

 by Murie, only the deepened furrows were covered with a dermal lattice-like network of 

 delicate hexacts, forming square meshes, he still regarded it as possible that the entire 

 surface of the whole sponge was covered with such a dermal network. 



Since I was able, in the British Museum, to examine some microscopic prepara- 

 tions, which were probably made from Murie's original specimen, and to compare the 

 loose spicules preserved in great abundance, and partly in their natural position, with 

 those which could be discovered here and there in the fragments from the Challenger 

 Expedition, I was able to demonstrate the most complete agreement between the two 

 forms. The identity of the species is therefore indubitable. 



The slender hexacts of the dermal skeleton are covered with small pointed tubercles, 

 especially on the extremities of the straight rays which run out to simple points. The 

 distal ray is shorter, the proximal longer than the four equal intersecting tangentials. 

 The outer extremity of every distal ray seems to be associated with a regular floricome- 

 like hexaster. In the best preserved portions I found these on almost all hexacts of the 

 dermal network (PL XCVIII. fig. 5). 



Each of the six strong round and moderately short basal rays bears six terminals, 

 which have the form of a liliaceous perianth, being slightly curved. They become 

 gradually thicker towards the outer extremities, and finally terminate in a spherical 

 knob. It seems to me noteworthy that these freely projecting spicules differ in the 

 formation of the outer extremities of their terminal rays from the true floricomes of 

 the Euplectellidse, &c., though they agree in position and general form (PL XCVIII. 

 fig- 6). 



In addition to the dermal hexacts with radial axial ray, strong dermal scopulte occur 

 with rough shaft and four strong almost parallel teeth, which are likewise rough, and 

 pass into a small terminal thickening (PL XCVIII. fig. 9). 



Between the beams of the lattice-like dictyonal framework, strong uncinates occur 



