ON ANORTHITE FROM MIYAKE JIMA. 45 



Explanation of the Plate I. 



Fig. 1. — A simple crystal of the first type in the position 

 adopted by Des Cloizeaux and vom Kath. On the face il/=010, the 

 direction of the Pericline-lamella?, or the trace of the " Rhombische 

 Schnitt" is indicated by fine lines, which make an angle of about -16 

 with the ed"e P : M. 



Fig. 2. — Same as fig. 1. A very common form of the first type. 



Fig. 3. — A horizontal projection of a crystal of the first type ; 

 the plane of projection perpendicular to the Brachyaxis. 



Fig. à. — Same as fig. 3, showing parallel intergrowth ; the 

 crystal is imperfect at the middle portion and an irregular attachment 

 of smaller individuals is observed in the specimen a. 



Fig. Ö. — A horizontal projection as in fig. 3, 4. Some imperfec- 

 tion is observed in the lower portion. 



Fig. 6. — A common form of the penetration-twin analogous to 

 the Carlsbad type. In this form it often happens that the faces o, ]), 

 are unequally developed on ditterent sides as in the figure. The 

 intersection-edges of o\ p, M' become very nearly parallel to those of 

 jP, e, M. 



Fig. 7 . — A rhomb-shaped modification of the twin, the same as 

 in fig. 6. The two individuals which are distinguished by the thicker 

 and the lighter lines, are composed of several subindividuals. The 

 faces 0, p, are developed on both sides very extensively, the edge P, d, 

 il/ becoming very nearly parallel to the edge o,p',j\l'. The projection 

 is made on a ])lane perpendicular to tlie edge P, x, //, of one individual, 

 so that the edge P, .t, // does not coincide exactly with the first. Tlie 

 face t becomes here relatively large, and ^ ery nearly parallel to y'. 



Fig. 8. — Horizontal projection of tlie twin, similar to those of 



