Geology and Natural History. 309 
lepis Agassizi Gein. ; and the Reptiles comprise the = ten Plesi- 
osaurus Bernardi Owen, Polyptychodon interruptus Owen e- 
lonia Carusiana Gei 
he work is full in ite — = acca a ed many of 
the species have been first made known by Dr. Gei 
17. Pa Mdtontologioal Cabinet of me Junk Ha 7 peat at 
Hall’s extensive collection of fossils has been purchased for the 
Central Park Museum, New York. The price reported to have 
been stipulated is $65,000. 
. On two new varieties of — by Prof. J. P. Cooxs 
and Mr, F. A. Goocs. (Proc. Amer. Acad. yr of May 11, 
1875).—In this paper, which may be regarded a s supplementary 
rmi es, one 
-Lerni, Delaware Co., Pa., and another from Pelham, Massachusetts. 
By means of careful experiments, the loss of water was — 
after air-drying, and at 100° C., 300° C. and red heat. The 
analyses obtained and those previously made of other ccocolieek 
are discussed, and the following el reat conclusions reached. 
- That all the vermiculites are unisilicates. 
- That these minerals combine with ane in several definite 
proportons—susaiing Prof. Cooke’s former — that the 
water in the iculites is water of erystallizati 
3. That ae? oar be reduced to the condition peach rh a 
atomic ratio (oxygen-ratio) for the silica, — and water, 
ons is therefore taken as the normal ra 
4. That the only essential differenc spt tween the different 
varieties of vermiculites is in the ratio bee the sesquioxide 
and protoxide bases. 
e atomic ratios obtained for the air-dried, dried at 100°, and 
dried at 300°, specimens, are respectively, fo for 
Halli 
Pelhamite 4:4:4, 4: 4:2, 
efferisite 4:4,4, mayen 
The Lerni mineral gave, dried a pee 6 rae yatio 2 :23+1 
(=4:4:2); and the analysis afforded sities of results) 
Si 38-03, £1 12-93, Pe 7-02, Fe 0:50, Mg 29° ~ “i pani se 
19. Dana’s System of Mineralogy.—A n 
this work—the ope as been prougirt- out out rein the er 
Messrs, Wiley & Son of New York; in other words, copies have 
been struck off from the plates after making a number of corr 
tions as in the case of the other “subeditions.” Moreover the 
copies of this subedition contain the two Appendixes to the work 
—the first by Professor Brush, and the second by Mr. E. S. Dana 
Piecaepe | thus 28 pages to the 828 of the —— 
ere gave lacustris, &e.—Som ount ome salaries 
upon this _Microscopic plant, sail upon the "foundations of a nat- 
Z “e <a il of DeBary—in the me rn oe — 
Cc: em £ tom. xix, . a 0, 
1875). re ns rear ot be a ( pp ee Pies wae 
