344 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Juiie 15, 



EXPLANATION OF PLATE XIV. 



Fig. 1. Lima Pontonis, Lycett. Fig. 6. Neaera Ibbetsoni, Morris. 



Fig. 2. Ceromya similis, Lycett. Fig. 7. Turbo gemmatus, Lycett. 



Fig. 3. Cyprina nuciformis, Lycett. Fig. 8. Cylindrites turriculatus, Lycett. 



Fig. 4. Tancredia axiniformis, Phillips, Fig. 9. Pliasianella Pontonis, Lycett. 



sp. Fig. 10. Trochus ornatissimus, D'Orb. 



Fig. 5. angulata, Lycett. Var, Pontonis, Morris. 



On the Insect Beds in the Purbeck Formation of Dorset 

 and Wilts ; and a Notice of the Ocaa-rence of a Neuropterous 

 Insect i7i the Stonesfield Slate q/" Gloucestershire. By 

 the Rev. P. B. Brodie, F.G.S. 



[The publication of this paper is deferred.] 



Description of the Remains of Fossil Insects from the Pur- 

 beck Formation q/" Dorset and Wilts, and from ^Ae Stones- 

 field Slate of Gloucestershire. By J. O. Westwood, 

 Esq. 



(Communicated by the Rev. P. B. Brodie, F.G.S.) 



[The publication of this paper is deferred.] 



4. On the Microscopical Structure of some British Ter- 

 tiary and Post-tertiary Freshwater Marls and Lime- 

 stones. By H. C. SoRBY, Esq. F.G.S. 



[Abstract*.] 



Th e author first described the general conclusions he had arrived at 

 with respect to the condition of the mineral portion of calcareous 

 organisms, which he considered is first deposited in the form of cry- 

 stalline granules of variable size, that afterwards undergo more or less 

 of crystalline coalescence. In some cases this scarcely occurs at all ; 

 but in others it does to a very considerable extent during the life of 

 the organism, and this produces a great difference in the character 

 of the particles into which it is resolved by decay. The falling to 

 powder that then takes place is the result of the oxidization and 

 removal of the organic portion, and, if no crystalline coalescence had 

 occurred, the shell or other body might be resolved into the very 

 minute, ultimate, crystalline granules ; whereas, if much coalescence 

 had taken place, it would break up into miich larger ones, showing 

 in many instances its minute organic structure. 



* The entire paper is not printed, by desire of the author, who intends publish- 

 ing a general account of the microscopical structure of British rocks, in a separate 

 form, with very numerous illustrations. 



