Penfield and Ford — Developments of Calcite Crystals. 243 



this type of crystal the rhombohedron s is prominent and is 

 bevelled by the scalenohedron v ; the pole edges of v are trun- 

 cated by the rhombohedron f, and B and e appear as slight 

 modifications only. The type of crystal, however, which it is 

 desired especially to call attention to is represented by fig. 15, 

 there being several almost ideally developed crystals of this 

 type in the collection. The peculiar feature presented by the 

 crystals consists in the termination of the prism m, 1010, by 

 twelve faces of almost equal size and shape, thus giving the 

 appearance of a prism terminated by a dihexagonal pyramid. 

 Six of these terminal faces belong to the positive scalenohe- 

 dron v, and the remaining six to the negative scalenohedron 

 B, while the negative rhombohedron e appears at the end of 

 the crystal. The distinction between the v and B faces is at 



\?> 



14 



15 



first glance not at all apparent, but the forms may be distin- 

 guished by their relative positions with reference to the rhom- 

 bohedron e and by slight differences in their surface markings, 

 the v faces being finely striated parallel to their intersection 

 with the unit rhombohedron, while slightly undulating, smooth, 

 vicinal surfaces characterize the form B. 



5. Crystals from El^olite-Syenite, Montreal, Canada. 



The crystals under consideration are small tabular individu- 

 als, fig. 16, measuring about 8 ram in 

 diameter, and were found by Mr. 

 W. F. Ferrier of Eossland, B. C, at 

 the Corporation Quarry, Outrement 

 near Montreal. Only a few crystals 

 were found, and one of these was 

 presented to the Brush collection by 

 Mr. Ferrier. A tabular habit is not 

 at all uncommon for calcite, but the crystals deserve brief men- 



16 



