118 SILICEOUS SPONGES. 



The ridges or folds of the outer surface are about 1 mm. in width, and the ovate 

 or somewhat irregularly elongate canal-apertures are from 1 to 2 mm. in length. 

 The octahedral nodes of tlie interior mesh are clearly shown ; the distance from node 

 to node is about '4 mm. 



There is but a single specimen in the Museum collection, which had been named 

 Spongia ramosa, Mantell ; but beyond its mode of grorwth it has no other character 

 in common with that species. 



Distribution. Grey Chalk: Dover. 



Genus CCELOSCYPHIA *, Tate, 1865 (emend. Hinde). 



This name was proposed by Tatef as a substitute for Polyccelia, FromentelJ, 

 which had been previously applied by Prof. King § to a genus of Actinozoa. As 

 repi'esenting a natural genus of sponges, PoTycoelia, From., is quite valueless, and 

 the forms included therein by Fromentel and F. A. Roemer have been placed by 

 Zittel in two or three genera. It is needless therefore to adopt Tate's suggestion 

 and substitute another term for a genus which is now obsolete. The particular 

 species, however, that Tate placed under Coeloscyphia appears to me to belong to a 

 distinct genus, and I therefore propose to retain his name for sponges with the 

 following generic definition : — 



Sponges consisting of simple cylindrical tubes growing from a common centre. 

 The walls of the tubes regularly folded so as to form vertical subparallel ridges with 

 intervening furrows. The spicular mesh with octahedral nodes. 



This genus is intermediate between Sestrodadia and PoJyhlastidium. The non- 

 branching character of the tubes and the vertical ridges of the wall distinguish it 

 from the former genus, whilst the absence of a common tubular axis separates it from 

 the latter. 



CcELOSCYPHiA SULCATA, Tate, sp. (Plate XXIX. figs. 1, 1 a.) 



1865. Cceloscyphia sulcata, Tate, Quart. Journ. Geol. Soc. vol. xsi. p. 43^ t. 5. f. 5. 

 1878. Coeloscyphia sulcata, Zitt. Stiidieiij III Ab. p. 31, note. 



The only specimen consists of three short subequal cylindrical tubes, 17 mm. in 

 length and 9 in width, growing from a common centre. No stem has been preserved, 

 but it is probable that one was originally present. The walls of the tubes are 

 folded so as to form 12 to 14 vertical ridges ; the intervening furrows are concealed 

 by the matrix, which also fills the cloacal tube. The cloacal aperture is circular, 

 and 3 mm. in width. The total thickness of the wall is about 3 mm., whilst the 



* This genus is unintentionally omitted from the list on p. 16. 

 t Quart. Journ. Geol. Soc. vol. xsi. p. 43. 

 X Introduction a Tetude des Eponges fossUes, 1859, p. 32. 

 § Annals & Mag. Nat. Hist. 184>J, 2nd ser. vol. iii. p. 388. 



