56 
Troost on the "Pyroxene, 
the four primitive sides very narrow, with summits of ten 
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. 
19. 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. Trisub tractive — 
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. ili. p. 130, pi, 3, fig". 6. 
f Mem. Mus. 3, p. 124, fig-. 2. 
^ Mem. Mus. p. 126, fig-. 4. 
