1879.] 169 [Halsted. 
sequently to the deposition. Prof.,Pumpelly, in his report on this 
district, repeatedly speaks of these as segregated masses, and some 
of his figures show this very clearly. These Iron Mountain ores are 
very often manganiferous, and in some cases the manganese oxide 
forms from twenty to eighty per cent. of the whole. 
The resemblance in modes of occurrence and structural peculiar- 
ities of the Iron Mountain and Lake Superior iron ores leaves little 
room to doubt that they are essentially similar deposits; and when 
the structure of the Marquette jasper ore, especially, is compared 
with that of many petrosilicious rocks, it is difficult to avoid the con- 
clusion that they have some community of origin. And then, too, the 
ordinary petrosilicious rocks are not entirely non-ferruginous, since 
they are often of a deep red or brown color, and, in eastern Massa- 
chusetts, at least, contain occasional strings and veins of hematite. 
Without claiming to have proved a connection between the strati- 
fied petrosilicious rocks with the associated iron and manganese 
ores, and the deep sea clays, I consider that the foregoing compar- 
isons show that there is no sufficient warrant for the statement that 
the modern abyssal accumulations are analogous to nothing now ex- 
posed to our observation among the older formations of the globe. 
CLASSIFICATION AND DESCRIPTION OF THE AMERICAN 
SPECIES OF CHARACEH. By B. D. HAtstTep.! 
The object of this paper is to present the results of a systematic 
study of the American species of Characee. In some cases the ma- 
terial at hand was not either in quantity or quality what one would 
desire in order to arrive at the most satisfactory conclusions. And 
again, owing to the unobtrusive habits of these plants, doubtless some, 
and perhaps many, species have still escaped the eye of the botanist 
or collector. , 
The principal material for study has been the large collection of 
undetermined American specimens in the Gray Herbarium. Besides 
this, private collections were kindly loaned by Dr. W. G. Farlow, 
of Harvard College, Professor Eaton, of Yale College, Professor C. 
E. Bessey, of Ames, Iowa, Dr. J. W. Robbins, of Uxbridge, Mass., 
Mr. John Robinson, of Salem, Mass., Mr. Chas. C. Frost, of Brattle- 
boro, Vt., and others, to whom my thanks are due. 
1 The present article forms a part of the thesis presented by the writer as a can- 
didate for the degree of Doctor of Science of Harvard University in May, 1878. 
