758 REVIEWS 
evidences of the care taken by the author to prevent errors on the part 
of the student, and, with the detailed methods of procedure described 
in the introductory chapters, it would seem as though everything had 
been done to enable the student to fit himself to identify minerals by 
all means except those based on their optical behavior in polarized light. 
A chapter has been introduced into this edition treating of the 
crystal forms of minerals in a manner especially adapted to beginners. 
The treatment is necessarily brief as regards the principles of crystal- 
lography. Particular stress has been put upon the illustration of the 
subject. The number of figures is not only large as compared with 
the extent of the text, but care has been taken to employ examples most 
likely to be met with by the student, and the drawing of the figures has 
been well done. ‘The method of treatment is mainly descriptive, and, 
though conceptions of symmetry are introduced, and excellent figures 
representing the relative positions of different axes of symmetry are 
given in connection with various subdivisions of crystal forms, the 
application of symmetry to the forms or its relation to them is left to 
the student to work out. The arrangement of the groups or systems 
of crystal forms is that ordinarily followed, beginning with those having 
the most complex symmetry, holohedral isometric crystals, and finish- 
ing with crystals without symmetry, the triclinic. Subdivisions of 
each of these systems are called normal, when holohedral according to 
former usage, and when having less symmetry than the highest in each 
system, that is, when belonging to what have been called hemihedral or 
tetartohedral, they are named after some characteristic crystal form or 
after some mineral characterized by such a form. 
In all parts of the book there are evidences of the great care taken 
by the author to render the subject intelligible to persons taking up 
the study of minerals for the first time, and there can be no question 
as to the success of the endeavor. Pals 
The Lower Cretaceous Grypheas of the Texas Region. By ROBERT 
Tuomas Hitt and THomas WayLanp VauGHAN. Bulletin 
IN@s UB, UG Ss GS,  \Wasiaimnetom, ID), ©, 
The bulletin presents a careful study of that group of fossil oysters 
which has generally been referred to Gryphea pitchert of Morton. The 
authors vigorously criticise the opinions and descriptions formerly 
