190 
SCIENCE. 
to be determined by the greatness of its magnifying 
power. On the contrary that instrument must be 
considered the most efficient which renders the details 
of an object perceptible with the lowest power. De- 
stinctness of definition, by which is meant the 
power of rendering all the minute lineaments 
clearly seen, is a quality of greater importance than 
mere magnifying power. Indeed, without this quality 
mere magnifying power ceases to have any value. 
At present there is an honorable competition 
between Spencer and Tolies, of America, Powell and 
Lealend, of England, and Zeiss, of Germany, as to 
who shall produce the most perfect microscopal ob- 
jectives; and it would be a difficult matter to decide 
which of these firms possesses the greatest merit in 
workmanship. Zeiss, with his oil immersion system, 
may have obtained the credit of a temporary advan- 
tage, but similar forms of objectives are now being 
manufactured in this and other countries with success. 
These makers are bringing to bear on their work 
all the most recent discoveries in optical science, and 
if any advance is made in the magnifying power of 
objectives, we shall expect to find it produced by 
such skilled opticians. 
PALAEONTOLOGICAL RESEARCHES. 
By Prof. Henry S. Williams, Ph. D., Cornell University. 
I. 
Genesee Slate. Fauna and Flora of Station xxxiv. d , H. S. W. 
On the eastern shore of Cayuga Lake, N. Y., near 
the head, is a fine exposure of the boundary strata of 
the Hamilton and Chemung periods. Careful exami- 
nation has been made of the upper part of the Gen- 
esee slate as it occurs in Burdich’s Ravine, the face 
of the high fall. (Station xxxiv. H. S. W.) Here 
the lowest Portage sandstone lies about 60 feet above 
the surface of the lake, and the characteristic Genesee 
slate follows immediately under it. The following 
species were obtained in the slate between four and 
five feet below the sandstone stratum, forming the 
base of the Portage group : 
Discina lodensis , Van. — abundant. 
Discina t rime at a. Hall — frequent. 
Lingula spatulata , Van. 
Lingula concentrica — (of Vanuxem’s Rep’t, but not 
Conrad’s species). See beyond. 
Tentaculites Jissurella H. — abundant. (See beyond). 
Leiorhynchus quadricostatus, Van. 
Chonetes lepida, Hall. 
Aviculopecten fragilis, Hall. 
Orthoceras — ( subulatum ?). 
Ambocoelia umbonata, Con. 
Avicula speciosa, Hall. 
Impression of part of Goniatites l . 
Plants, three well marked forms. 
This fauna has several interesting forms in it. 
The recurrence of Marcellus forms noticed by 
Hall, in Geol. 4th Dist. N. Y., p. 222, 1843, ’ s seen 
to be more marked than was observed by him. 
The Tentaculites Jissurella, Hall, may prove to be 
Styliola (2 /.) but if so, the same form is repeated in 
tire Genesee slate from the Marcellus shale. 
It is difficult to be satisfied with the recognition of 
this form in Styliola, since annulated forms occur to- 
gether with the smooth ones, and except in the annu- 
lations are not to be separated from the true Styliola 
forms. The shells are very frail and crushing may 
account for the longitudinal folds in part, as it does in 
some of the Orthoceratidae. 
This fact is noticed by Hall in the Marcellus forms 
(in Illustrations Her Fossils, PI. xxvi.) and the “pre- 
vailing form,” fig. 14, is the prevailing form in the 
Genesee, and among the specimens just collected the 
annulated forms do not differ in size from the smooth 
ones, and the latter are often larger. 
Discina lodensis, Van. occurs in abundance, and with 
some variation, but the form called D. truncata, H. is 
distinct and does not show gradation into the former. 
Still this is also distinct from the Lingula which Van- 
uxem figured, but did not describe in Geol. of 3d 
Dist., N. Y., p. 168, fig. 4. Vanuxem refers the 
species to Conrad’s Lingula concentrica, which is evi- 
dently a mistake since Conrad’s species, Z. concentrica, 
is from the Helderberg mountain, in limestone, and is 
£ inch long (see Geol. Rep’t, N. Y., 1839, p. 64). The 
species found in association with Z. spatulata is nearly 
5 millemetres long and 3.3 mm broad, and the cardinal 
margin is broadly, evenly rounded, and not attenuated 
as in spatulata. 
L. spatulata, Van. is nearer the size figured by both 
Hall and Vanuxem (from 4 to 4.5““) instead of ap- 
proaching 7.5“” (,i- inch) as stated by Hall in the de- 
scription (Pal. of N. Y., vol. 4, p. 13). These are of 
the ordinary size of Lingula spatulata , Van. as they 
have been observed by the author. The Lingula con- 
centrica (of Van. not Con.), is distinguished from the 
Discina truncata by the absence of the indentation or 
truncation, and the extension of the margin beyond 
the umbo, as well as other characters not as easily 
observed. 
The Chonetes found is distinctly the Chonetes lepida 
of Hall, and not setigera. Still this may prove a 
variety of setigera upon further study ; the two occor 
together in the Moscow shales and Marcellus, and in 
other strata of the Hamilton. 
Only a single specimen of Aviculopecten fragilis was 
found, but this distinct and characteristic. 
