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LVI.— ON AN HEXACTINELLID SPONGE FEOM THE GAULT, 

 AND A LITHISTID FEOM THE LIAS OF ENGLAND. 

 By PEOFESSOE W. J. SOLLAS, M.A., D.Sc (Plate 

 XXL) 



[Read, February 16, 1885.] 



Fossil sponge remains are exceedingly rare both in the Lias and 

 Grault deposits of Europe. Fragments of sponge-skeletons and 

 scattered spicules have been described from Liassio strata in Aus- 

 tria, and occasional spicules are met with in the English Lias ; but 

 hitherto no entire sponge. 



The Gault of Cambridge contains not uncommonly so-called 

 " coprolites," which have every external appearance of sponge- 

 remains, but which on the other hand are usually devoid of inter- 

 nal structure. 



The discovery by the Rev. P. B. Brodie, m.a., f.g.s., of two 

 complete and sufficiently well-preserved sponges, one from the Lias 

 and the other from the Grault of England, is consequently of con- 

 siderable interest ; Mr. Brodie, recognising this, has placed his 

 specimens in my hands for description, and I now offer the fol- 

 lowing account of them, commencing with the specimen from the 

 Lias : — 



Platychonia brodiei (sp. n.). 



Sponge, irregularly pouch-shaped; higher on one side, which 

 is 55 mm. in length, than on the other, which measures 23 mm. 

 in length. Central cavity large, 31 mm. across. Wall of slightly 

 variable thickness — about 8 mm. where highest, and 10 mm. 

 where lowest : both surfaces uneven, with irregular elevations and 

 depressions ; otherwise smooth. Ostia small ; on the outside, from 

 about O'l to 0'15 mm., round or oval ; on the inside, 0*1 to 0*4 

 mm. in diameter, round, oval, or irregular ; without a raised 

 margin, even with the surface. 



Canal System. Fine and irregular. Small canals rarely enter 

 the wall perpendicular to the surface, and, when they do so, lose 

 themselves in the interior. No vertical tubes. 



