204 Miscellanies. 



ing to this test, unquestionably belonged to the latter class, and that it 

 most closely resembled Sphyrcena among recent fishes in its dental struc- 

 ture. 



The second instance was the Basilosaurus of Dr. Harlan, which has 

 been referred to the class Reptilia; and the double-fanged structure of its 

 teeth had, on the strength of its supposed saurian affinities, been adduced to 

 weaken the arguments advanced in favor of the mammiferous nature of 

 certain fossils from the Stonesfield oolite. Mr. Owen, after describing the 

 microscopic character of the teeth of the Basilosaurus, shewed that it de- 

 viated from the saurian structure in this respect as widely as the Sauro- 

 cephalus, but that the modifications of its dental structure resembled most 

 closely that of the Cachalot and herbivorous Cetacea. Lastly, Mr. Ow- 

 en alluded to the difference in the views entertained by Cuvier and M. de 

 Blainville, as to the affinities of the Megatherium, which was referred by 

 the one to the family of the sloths, and by the other to that of the arma- 

 dillos ; after explaining the well marked differences in the microscopic 

 characters of the dental structure in these two families of the so-called 

 Edentata, Mr. Owen proceeded to describe the structure of the teeth of 

 the Megatherium, and to shew that in its close resemblance to the dental 

 structure of the sloths, it confirmed the views of the great founder of the 

 science of fossil remains. This paper was accompanied by a number of 

 very beautiful illustrative drawings, exhibiting the minute structure of the 

 teeth of the animals referred to. 



Mr. Jackson then read a short paper, drawing the attention of the So- 

 ciety to a mode of mounting the compound microscope, which differs 

 in some particulars from the methods generally adopted. The principal 

 object to be kept in view in the construction of the instrument, is the 

 prevention of those accidental vibrations which so much interfere with 

 microscopic examinations, especially in the neighborhood of crowded 

 thoroughfares. This object is effected by connecting together the body 

 and the stage of the instrument in such a manner, that whatever vibra- 

 tions are communicated to the one shall be equally communicated to the 

 other. In the instrument of Mr. Jackson, this principle has been carried 

 further than has hitherto been effected ; and it also affords improved fa- 

 cilities for minute adjustments, and the accurate admeasurement of mi- 

 croscopic objects. 



A discussion ensued on the subject of Mr. Jackson's paper, and also 

 on the best modes of measuring microscopic objects, and the greater dif- 

 ficulties encountered in ascertaining the antero-posterior diameters of mi- 

 nute bodies, as compared with the facilities which we possess of obtaining 

 lateral measurements. The meeting then resolved itself into a conver- 

 sazione, during which a number of interesting objects were exhibited by 

 individual members, many of whom had their microscopes upon the ta- 

 ble. The meeting adjourned at 11 o'clock. 



