250 BRITISH JURASSIC SPONGES. 
sand, oolitic grains, and broken-up fragments of crinoids or other Echinoderms. 
In outer form some are as perfect as recent specimens, and their spicular 
structure has been preserved almost unaltered and uninjured in spite of the fact 
that their constituent spicules are exceedingly slender, fragile, and minute, and 
that they are only loosely and irregularly intermingled together. The spicules 
are now somewhat more brittle than those of existing Calcisponges, their surfaces 
are smooth and without trace of erosion, and they have the same general appear- 
ances under the microscope and in polarised light as recent Calcisponge spicules, 
though they are hardly so lustrous. 
Distribution.—Marl|stone of the Middle Lias; zone of Ammonites spinatus, at 
King’s Sutton, Northamptonshire, associated with Foraminifera, Corals, Mollusca, 
and Polyzoa. These sponges were discovered by Mr. E. A. Walford, after whom 
the species is named. 
