J. S. Gardner — On the Gault RosteUarice. 161 



Figs. 3, 4, 5. — Crystalline grains of olivine replaced by chlorite, and inclosing (No. 

 5) magnetite crystals. From Upper Trap -band, Rathjordan. 



Figs. 6, 7, 8. — Cells in amygdaloid, filled with green chlorite (or epidote) and calcite. 

 In No. 7 the green mineral has an excentric arrangement. The calcite is 

 colourless, with a peculiar banded structure, and iridescent to pearly lustre. 

 Cahermarry. 



Fig. 9. — Portion of glass base — magnified about 200 diameters — showing tubes, 

 cells, and belonites, and inclosing crystals of magnetite. From Upper 

 Trap-band, Rathjordan. 



Fig. 10. — Twin crystals of hornblende, brownish colour, inclosing magnetite 

 grains. Lower Trap-band, Roxborough. 



Fig. 11. — Pseudomorphous crystal after hornblende, the substance of the mineral 

 replaced by chlorite or epidote, and calcite. Roxborough. 



Figs. 12-18. — Forms of augite crystals, or pseudomorphs, mineral sometimes re- 

 placed by chlorite and calcite, as in Figs. 12, 13, 14, 15, and 16 ; from 

 Bally brood. Fig. 17 represents a crystal of augite from Upper Trap- 

 band, Ballytrasna. Nos. 13 and 15 are twin crystals. 



The figures have been sketched by the hand direct from the microscope by the author. 



IV. — Notes on the Genus Bostellaria (or Aporruais?) of the 



Gault, 

 By J. Starkie Gardner, F.G.S. 



HAVING read Mr. Price's note and description of Bostellaria 

 maxima in last month's Number (p. 97, PL VI.), I venture 

 to express my regret that so doubtful a species should be published 

 with the apparent authority of the Geological Magazine to confirm 

 it ; especially as Mr. Wiltshire (than whom there is no one better 

 acquainted with English Cretaceous MoUusca) is of opinion that it is 

 only a giant form of Bostellaria carinata. The description given by 

 Mr. Price would equally apply to the ordinarj'- form of B. carinata 

 which occurs in the same bed, and, save in size, exactly resembles it. 

 The most distinctive portion of the shell, the wing, is unfortunately 

 not preserved. The examples of Bostellaria carinata found in this 

 bed, I may remai'k, always differ slightly in form, being broader 

 and more obtuse (they are also usually more crushed and imperfect) 

 than those from the lower beds. I am fully convinced that, if size 

 alone is sufficient ground to justify the formation of new species, we 

 shall speedily find the present confusion of names in the Gault fauna 

 more hopelessly involved and more impossible to unravel than ever. 

 What, for instance, would be the result of the adoption of such a 

 basis of nomenclature for the Cephalopoda from the same formation ? 



But, even if the species be allowed to remain, I cannot see how 

 the publication of an isolated form can add materially to our know- 

 ledge, since no monograph of Cretaceous Eosie//an« has been published, 

 and many of the comparatively common species are still imperfectly 

 or Improperly described. 



While considering the subject of Bostellaria, 1 should particularly 

 like to obtain the opinion of workers in recent and fossil conchology 

 as to the advisability of adopting Da Costa's name of Jporrhais for 

 the group, and whether it might not even be made to include 

 Pteroceras Fittoni of the Lower Greensand, and Pteroceras bicarinata 

 or retnsa of the Gault. I subjoin an abbreviated translation of Pictet 

 and Campiche's description of each genus : 



VOL, X. — NO. CVI. 11 



