504 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 5U. 



In single crystals or those of a single specimen or cavity almost any 

 form may be etched to complete dullness. The forms of the clino- 

 dome zone are almost invariably brilliant and free from etching of 

 any sort, yet on one crystal measured the form g (012), present as a 

 large face, was entirely dull. As before stated, various other irregu- 

 larities occur, but not with sufficient regularity to be of value in form 

 identification. Many of the other forms are characteristically etched, 

 but these occur as faces too small to be of value in orienting the 

 crystals. 



FORMS. 



Whitfield described the following 27 forms on datolite from West- 

 field: 



a (100), I (010), c (001), m (110), r (230), o (120), x (102), v (103), 

 m x (011), g (012), Q (018), t (013), n (111), v (Til), e (Tl2),X (113), 

 fi (T14), k (115), Q (122), (121), M (T22), i (123), a (124), e' (T48), 

 X' (149), m' (1.4.10). 



Of these M (122), e' (T48), X' (149), and ]i' (T.4.10) were new to 

 the species. 



Kraus and Cook confirmed all forms observed by Whitlock except 

 X' (149) and fi (018) and added as forms new to the locality I (130), 

 b (223), 7r (231), u (104), £ (102) and as forms new for the species m 7 

 (067), m z (0.1.10), n y (1. 1.10). 



Gorgey and Goldschmidt observed 45 forms, of which 1 1 were new 

 to the locality, namely: 



a (014), 2 (302), n (T01), q (312), n (132), T(214), U (123), B (T21), 

 N (322), r (314), x (534), and 8 new to the species, namely: 



<p (308), P (332), b (T18), H (131), <K (T26), 33* (313), £ (454), 

 t) (911). 



Ungemach found 60 forms, of which the following 6 were new for 

 the locality: 



^ (201), 7? (410), A (210), co (116), Y l (T34), d (T35), and 9 which 

 were new to the species, namely: 



y (601), j (502), Tc: (3.0.10), s (530), 6 (140), E (T36), /• (412), 

 (546), \) (811), ? (TT.0.2). 



Thus at the beginning of the present investigation there had been 

 reported on datolite from this locality 68 forms, of which 24 were 

 new to the species. The present writer has recognized on the 

 crystals studied during the present investigation 104 forms, of which 

 10 are new to the locality, as follows: 



p (106),/ (203), _s (302), z (201), A (112), M x (231), ft (454), 

 r (132), E (T38), Mi (227), and 46 forms which are new for the species, 

 as follows: 



(S (380), 3 (043), 2 (205), vie. (16.0.39), 3)1 (403), (12.0.25), 

 O (134), %\ (192), C (1.10.2), ft (1.12.2), © (331), Z (343), U (344), 



