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 Tolles. 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. 



PAL^EONTOLOGICAL 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 : 



Piscina lodensis, Van. — abundant. 



Discina truncata, I fall — frequent. 



Lingula spatulata, Van. 



Lingula concentrica — (of Vanuxem's Rep't, but not 

 Conrad's species). See beyond. 



Tentaculitesfissurella If. — abundant (See beyond). 



Leiorhynchus quadricostatus, Van. 



Chonetes lepida, /At//. 



Aviculopecten fragilis, J '/<///. 



Orthoceras — ( subulatum ?). 



Ambocoelia umbonata, Con. 



Avicula speciosa, Jlall. 



Impression of part of Goniatites ? . 



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, is seen 

 to be more marked than was observed by him. 



The Tentaculites fissurella, Hall, may prove to be 

 Styliola (2/.) but if so, the same form is repeated in 

 the 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 Der Fossils, PL 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, L. 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 L. spatulata is nearly 

 5 millemetres long and ^-3 mm broad, and the cardinal 

 margin is broadly, evenly rounded, and not attenuated 

 as in spat/da/a. 



L. spatulata, Van. is nearer the size figured by both 

 Hall and Vanuxem (from 4 to 4.5""°) instead of ap- 

 proaching 7.5'"'" (-3 ir 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. 



