HYALONEMA (PRIONEMA) SPINOSUM. 273 



terminal cone in H. validum, and are slender and have a very slender and fine- 

 pointed terminal cone in H. (P.) azuerone. 



Hyalonema (Prionema) spinosum, sp. nov. 

 Plate 48, figs. 1-31; Plate 49, figs. 1-2.3; Plate 50, figs. 1-5. 



Three specimens of this species were trawled nearly under the ecjuator in the 

 Eastern Pacific at Station 4742 on 15 February, 1905; 0° 3.4' N., 117° 15.8' W.; 

 depth 4243 m. (2320 f.); they grew on very light, fine Globigerina ooze; the 

 bottom-temperature was 34.3°. 



The microhexactines bear unusually large spines. To this the specific 

 name refers. 



Shape and size. The largest specimen (Plate 48, fig. 12) is a lamella or 

 plate, roughly round in outline when spread out flat. It is 46 mm. long, 37 mm. 

 broad, and has a fairly uniform thickness of 8-10 mm. The margin is rounded. 

 The lamella is folded along a straight line passing nearly through its centre. 

 The two parts on either side of the fold are flat, and enclose an angle of about 

 70°. On the convex side of the fold a rounded protuberance arises near the 

 margin. In life, the stalk, which is now, however, entirely absent, arose from 

 this. At the opposite end of the fold the margin is slightly incised. On the con- 

 yex surface of the lamella, which is the dermal, the covering (dermal) membrane 

 is lost in many places, and this side consequently appears rough and porous. On 

 the opposite, concave side, which is the gastral, meandric branching grooves are 

 observed, which, on the whole, radiate from a point in the fold near the centre 

 of the lamella. At this point a small and slender gastral cone arises from the 

 concavity of the fold. 



One of the smaller specimens (Plate 48, fig. 11) is lenticular in shape. It 

 measures 35 mm. in horizontal diameter and is 16 mm. thick. Near the middle 

 of one (the lower, dermal) face a rounded protuberance arises. From this, in 

 life, the stalk, which is now absent, protruded. In respect to the structure of 

 the surface this specimen resembles the large one. The other small specimen is 

 fragmentary and measures 25 by 22 by 8 mm. 



The colour of the two better preserved specimens is, in spirit, light brown; 

 of the fragmentary one, whitish. 



The lamellar or lenticular sponge-body is traversed by wide canals (Plate 48, 

 fig. 13), most of which extend in a more or less vertical direction. Some of these 

 canals are afferent and open out below, others are efferent and open out above 



