HAPLISTION. 147 



28. Haplistion Armsteongi, Young and Young. Plate V, figs. 1, 1 a, 1 b. 



1877. Haplistion Armstbongi, Young and Young. Ann. and Mag. Nat. Hist., 



ser. 4, vol xx, p. 428, 

 pi. xv, figs. 31—37. 



1878. Dysidea antiqua, Garter. Ann. and Mag. Nat. Hist., ser. 5, vol. i, p. 139, 



pi. x, figs. 7, 8. 



1879. Spongelia antiqua, F. E. Schulze. Zeitsch. d. wiss. Zool., Bd. xxxii, 



p. 126. 

 1883. Haplistion fractum, Hinde. Cat. Foss. Sponges, p. 207, pi. xxxviii, 



figs. 4, 4 a. 



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 



