534 PROCEEDINGS OP THE AMERICAN ACADEMY. 



755 



Average <p or 180° -<£ = 37° 26' 42° 14' 37° 40' 42° 11' 



The agreement between measured and calculated angles is here fairly 

 satisfactory and the form seems assured. 



X (322) has been reported only once on epidote from Elba by A. 

 Artini * who measured a single bright face agreeing well with its cal- 

 culated angle. 



It was found here on a single crystal with one measurable face, but 

 was noted frequently as a dull face in the zone [221 to T01]. 



322 



y (211) and R (411) were the commonest forms of this series and 

 were well determined by measurem ;nt on several crystals. 



* (513) present only on one crystal (figure 7) as a small face. 



Several of the above forms are lacking in the Winkeltabellen of 

 Goldschmidt, and as the various values there given have been calculated 

 for each of them they are given in the following table, which also 

 includes two forms for which certain values were found to be incorrectly 

 stated in the Tabellen : 



86 X 322 38 13 66 29 54 53 6101 34 34 46 05 1.4220 1.8057 2.2983 



The drawings show the extremely variable habit of the crystals. 

 Figure 1 represents perhaps the commonest type, a tabular twin 

 crystal, the two individuals entirely symmetrical to the twinning plane 



* Mem. Acad. Lincei. 4, 380, 1887. 



t Correction, Winkeltabellen, p. 130, line 32 from above, col. 10. 



\ Correction, Winkeltabellen, p. 131, line 12 from above, wbole line. 



