CALCITES OF NEW YORK 69 
SUMMARY OF MEASURED AND CALCULATED ANGLES (continued) 
Type IV 
LETTER ANGLE Beet | MEASURED | CALCULATED 
fo) / | ° / 
fy 6 iia 1011 : 4041 8 RM Oe athena Se MOF 
jouenaes 1011 : 8081 5 leas Seana Samia ears Saeees 0) 
(Ds S the NOI 1G), 0). 1063, th 10 bel 35 41 46 
p.:b 1011 : 1010 7 ASS ores 45 234 
lo\ak ee 1010 : 1012 2 63 41 63 45 
Vf ca §.8.16.3 :8.8.16.3 3 24 Bo || 24 46 
se ace SoS. IOB 2 MGS S83 2 Dota Ae 2. 58° 28 
EG ea Kesr ZS te 23 5) (owe 22 (2 
alge 3 4371 : 4731 1 GS SO | 68 21 
Wiese 3145 : 3415 a AOR eC AG ite!| 49 224 
Ket PS, 8 SD! 2 35 34 30 ~©=—30 
eee te. 6281 : 8261 3 27 27 BG Bl 
Was enw 3145 : 4135 9 1G 0) 16 04 
Vee 8 IKE PUB § IPBIL 10 47 5 47 14 
Aiea kes ABIL 8 BALL 8 22 11 Pil 74 
Saray 6281 : 268T 3 30 9 30 ©6— «62 
falg § sam,” «| 4041 : 0441 1 65 47 65 50 
fag, GIR 4041 : 2131 1 Dd 22 53) ARS 
am, 3} 4041 : 6281 4 14 51 | 14 59 
Pee S AP NGE2OR Se 20) 6,453 3 21 38 21 30 
Re Be APNG 20 non 16.4) 2003) 1 Ant yy) 42) 2 
Twinning 
Plate 4, figures 2-6 
Twinning parallel to the basal plane is characteristic of the larger 
crystals of the four types. In many instances, as in figures 2 and 5, the 
interpenetration of the two individuals results in the lateral development 
of one of them to the extent of forming deep reentrant angles between the 
planes of p. The crystal shown in figure 3 on which the basal plane of 
one individual is developed to a considerable habit, shows a low rim bound- 
ing the equilateral triangle formed by the intersection of the base. The 
inside faces of this rim, which is .5 millimeters high compared with a length 
of 14 millimeters for each side of the triangle, are formed by the planes of 
6.(0112). A similar crystal from Rossie is figured by Dana.! Other expres- 
‘Dana, J. D, System of Mineralogy. ed. 5, 1868. p. 676, fig. 579, 
