23 



marginal teeth, which are rather narrow and terminally lancet-shaped (pi. XVIII, 

 f. 18). 



The second variety of macramphidiscs is considerably smaller, only 80-100 /^ 

 long, has flatter terminal discs with 5, more rarely 6, broad and spade-like mar- 

 ginal teeth, and a cylindrical shaft, covered with more or less numerous, rounded 

 tubercles (pi. XVIII, f. 15-17). This variety occurs scattered singly in the 

 parenchyme and in the walls of the larger canals and is also met with in o-reat 

 numbers in the dermal and gastral membranes, where these spicules are placed 

 vertically to the surface, one half being imbedded in the sponge, the other half 

 projecting freely beyond it (pi. XVIII, f. 3). 



The mesamphidiscs principally occur in the walls of the larger canals where 

 they are vertically placed like the macramphidiscs in the dermal reticulation- 

 They vary considerably in size, and measure 4-0-70 ^ and more in length. The 

 shaft is slender, cylindrical and spined ; in the centre there is an annular thicken- 

 ing or a whorl of usually four crosswise-arranged spines ; the other parts of the 

 shaft are covered with irregularly-scattered, smaller, sharp tubercles. The 

 deeply beU-shaped terminal discs usually have 10 narrow and long marginal teeth 

 (pi. XVIII, f. 4-6). 



The micramphidiscs have the usual shape and size. They are 20-40 /* long 

 and very numerous in the dermal and gastral membranes ; less frequently they 

 occur in the parenchyme and in the canal- walls. 



As the root-tuft or peduncle is missing in all the three specimens, I cannot 

 say more about it than that the size of the cavity in the lower end of the sponge 

 which was occupied by the upper end of the peduncle allows one to assume that 

 it was 8 mm. thick. 



Acanthophores are numerous in the elevated margin surrounding the entrance 

 into the peduncle-cavity. They are mostly stauractines and diactines of various 

 sizes, covered with stout spines. Scattered here and there, particularly below 

 the gastral membrane, spheres, composed of concentric layers of sihca (silica- 

 pearls) are met with. These interesting structures (pi. XVIII, f. 12) measure 

 120 /A and more in diameter. They resemble the silica-pearls found and des- 

 cribed by me in other species of Hexactinellida. 



This species was found in the Bay of Martaban 13° 7' N., 94° 44' 15" E., in 

 a depth of 1171 m.=661 fths. 



Hyalonema alcocki F. E. Sch. 

 Plate VI, figs. 1-8. 



1895 Hyalonema alcocU F. E. Sch. in Abh. Preuss. Ak. 1894 pp. 34-37, Taf. VII figs. 1-8. 



I name this species Eyalonema alcocki in. honor of Dr. A. Alcock, who col- 

 lected most of the Indoceanic deep-sea sponges here described. It resembles 



