56 Troost on the Pyroxene. 



the four primitive sides very narrow, with summits of tea 

 faces. This is the habitual form of the Pyroxene diopside. 



17. Senobisunitary P.* A six sided prism, with sum- 

 mits of three faces. This is the form of the P. baikalite. 



18. Senoquaternary P.t The physiognomy of this crys- 

 tal differs entirely from the former varieties. It is a short 

 four sided prism, terminated by long sharp pyramids with 

 four faces. This, and the following form, belongs to the 

 P. fassaite. 



1 9. Duovigesimal P. % The former, having the pyramid 

 emarginated. 



To which number may be added the 



20. Periorthogonal P. 



21. Stomonomal — 



22. Analogical — 



23. Quadrioctonal — 



24. Binotriunitairy — 



25. Bisoctonal — 



26. Bisunibinairy — 



27. Trisubtractive — 



and those of which I have given the description in the Jour- 

 nal of the Academy of Natural Sciences of Philadelphia. 



28. Pyramidal P. An eight sided prism, terminated by 

 a four sided pyramid — from Franklin, N. J. 



29. Uniternary P. A flat six sided prism, with sharp 

 diedral summits — from Franklin, N. J. 



* Mem. Mus. vol. iii. p. 130, pi. 3, fig. 6. 

 f Mem. Mus. 3, p. 124, fig. 2. 

 i Mem. Mus. p. 12ft, fig. 4. 





