1872.] S0LLAS ITPPER-GEEENSAND C0PR0TJTES. 79 



from their walls to their centres, thus forming a radiating mass of 

 crystals ; it is well known that crystals arranged in this manner 

 will produce the phenomena described. 



Behaviour with Hydrochloric Acid. — Hydrochloric acid dissolves 

 the coprolites, some undergoing solution more readily than others, 

 owing to their containing a larger quantity of calcic carbonate. 

 While dissolving they emit a smell almost precisely resembling that 

 of petroleum. The hydrocarbons which produce this odour must 

 exist previously as gases, or combined with the calcic phosphate of 

 the coprolite. I believe that they are present in the latter condition. 

 The insoluble residue left on solution very frequently contains sponge- 

 spicules and siliceous organisms ; these may be separated in the 

 same way as Foraminifera are obtained from a piece of chalk. 



Enumeration of Genera *. 



Genus 1. Rhabdospongia. Sponge more or less rod-like, 1" to 2" 

 long, i" to |" diameter. Frequently attached at one end. Cloaca 

 none, solid throughout. Spiades filiform, acerate, sinuous. Species : 

 R. communis. 



Genus 2. Bonneyia. Sponge cylindrical to clavate, size variable. 

 Cloaca : longitudinal axis always occupied by a cloacal cavity from 

 5 to | of the whole diameter of the fossil. Spicules few. Species : 

 B. bacilliformis, B. cylindrica, B. Jessoni, B. scrobiculata, B. verron- 

 giformis. 



Genus 3. Acanthophora. Sponge massive, lobose. Spicules 

 acerate, fusiform, spiculated porrecto-ternate and recurvo-ternate, 

 triradiate, hexaradiate. Species : A. Hartogii. 



Genus 4. Polycantha. Sponge ovate. Cloaca present. Spicules 

 acerate, defensive, triradiate, quadriradiate, hexaradiate. Species : 

 P. Etheridgii. 



Genus 5. Betia. Sponge cylindrical or hemicylindrical, marked 

 on surface with a symmetrical fibre-like reticulation. Spicules few 

 or absent. Species : R. simplex, B. costata. 



Genus 6. Hyxospongia. Sponge large and massive. Cloaca 

 always present. Surface covered by a bark-like exterior, beneath 

 which it is smoothly and longitudinally striated. Species : H. patera, 

 H. calyx, H. Brunii. 



Discussion. 



Mr. Charlesworth complained that the author had not fully 

 stated Dr. Bowerbank's views, which were founded on the fact that 

 flint, wherever found, whether in fissures, the interior of organisms, 

 or elsewhere, always presented under the microscope a reticulated 

 structure. He had himself combated the view that flint was in all 

 cases silicified sponge, and had demonstrated that certainly, in some 

 cases, flint had been formed without the intervention of sponges ; 

 for in the case of the teeth in a lower jaw of a Mosasaurus found 

 in the Chalk, he had found the pulp-cavities completely filled with 



* Mr. Ethei'idge, after an examination of specimens, says that he entirely 

 approves of these generic groupings. 



