Troost on the Pyroxene. 55 



9. tfubtractive P.* The Bisu nitary, or the preceding, 

 Having the sharp angle of the summit replaced by a tri- 

 angular face, being sometimes undulated or curvilinear. 



10. Ambiguous P.t The former, in which the triangu- 

 lar face is so much enlarged as to make the two faces of the 

 summit disappear. 



11. DioctxdralV.% The variety Triunitary, having the 

 edges of the terminal faces emarginated. 



12. Epimeridal P. || An eight sided prism, with a sum- 

 mit with five faces. This is the form of the white Py- 

 roxene of the United States. 



13. Octo-duodecimal F '.§ An eight sided prism, with a 

 summit of eight faces. 



14. Trioctonal P. IT An eight sided prism, with a sum- 

 mit of eight faces — from Connecticut, United States. 



15. Stenomonal P.** Eight sided prism, with summits 

 of eight faces. 



16. Octo-vigesimal P.tt An eight sided prism, having 



* Traite, fig. 142. f Mem. Mus. 1, p. 284, fig. 27. 



i Traite 3, p. 85, fig. 143. 



H Annal. Mus. vol. xix. p. 257 — vol. xiv. fig. 1. 



§ Annal. Mus. vol. ix. et Jour. Min. vol. xxiii. p. 152, pi. 3, fig. 5. 



1 Jour. Min. vol. xxiii. p. 152, pi. 3, fig. 6. 



** Mus. 1, p. 289, pi. 14, figs. 31, 32. Ttie varieties Epimeridal and 

 Stenomonal show the truth of the remarks of Mr. Hauy regarding the 

 var. Octo-vigesimal, in the Jour, the Museum. — This crystal offers a re- 

 markable instance of those whims of crystallization happening in con- 

 sequence of certain faces being more or less distant from the centre — 

 the deviation originating in some of the faces having increased in size 

 at the expense of others, which change the entire aspect or physiogno- 

 my of the crystal, so that it is with difficulty that we recognize the same 

 type of the crystal. 



ft Annal. Mus. vol. ix. et Mem. Mus. 1, p. 290, pi. 14, fig. 33. 



