HAPLISTION. 147 
28. Haptistion Armstroncl, Young and Young. Plate V, figs. 1, 1 a, 1 0. 
1877. Hapnistion Armsrronat, Young and Young. Ann. and Mag. Nat. Hist., 
ser. 4, vol xx, p. 428, 
pl. xv, figs. 31—37. 
1878. Dystpra antiqua, Carter. Ann. and Mag. Nat. Hist., ser. 5, vol. i, p. 139, 
plex, fest 75.8) 
1879. Sronertia antigua, F. H. Schulze. Zeitsch. d. wiss. Zool., Bd. xxxii, 
p. 126. 
1883. Hapnistion rractumM, Hinde. Cat. Foss. Sponges, p. 207, pl. xxxviii, 
figs. 4, 4a. 
Fairly complete specimens are sub-spheroidal or ovoid in form, and apparently 
free. The type-specimen is 16 mm. in length by 13 mm. in thickness. The 
reticulating fibres vary from ‘14 to *5 mm. in thickness ; they form a network with 
circular, oval, or irregular polygonal apertures, ranging from ‘55 to 1 mm. in 
width ; in the interior of the specimen the meshes are somewhat more open than 
at the surface. The conical projections in which the fibres terminate are nearly 
equal in length, and approximately at right angles to the surface of the Sponge. 
The spicules are thickly disposed on the surface of the fibres, they are straight or 
slightly curved, apparently terminating bluntly. The longest spicule noticed 
measures ‘32 mm., whilst they vary from ‘025 to ‘04 mm. in thickness. 
Perfect examples of this species are extremely rare; as a rule only small, 
broken up fragments of the fibres are met with. The outer surface of the fibres 
has generally a brownish appearance, and when fairly well preserved shows the 
outlines of the component spicules on the exterior. The interior portion of the 
fibres is of solid white silica, probably resulting from the fusing together of the 
original spicules. The spicules on the surface are only shown as the result of 
weathering, they have an eroded granular aspect ; and, owing to the manner in 
which they overlap and are partially fused together, it is difficult to ascertain their 
perfect forms. In specimens which have been subjected to a greater degree of 
weathering the brownish tint of the fibres is changed to a rusty yellow, the 
outlines of the spicules have disappeared, and the surface of the fibres, and often- 
times the interior as well, consists apparently of minute, irregular granular 
particles of silica, partially cemented together. In this condition the fibres have 
somewhat the appearance of those of the existing genus Dysidea, and on a specimen 
thus preserved Mr. Carter based the species Dysidea antiqua. I am indebted to 
Mr. J. Thomson for the opportunity of examining the type form described by Mr. 
Carter, which corresponds in every respect, except in its condition of preservation, 
with the type of Haplistion Armstrongi. The spicules obtained by Mr. Carter from 
