1871.] 189 [Putnam. 



allel stride crossing each other at an angle. This paper ex- 

 cited much discussion among Microscopists, and the majority 

 of students now hold that these exclamation marks are prob- 

 ably illusive, while the true structure of the scale is still 

 doubtful. Mr. Stodder believed that these markings, what- 

 ever their nature, are confined to one surface of the scale. 



Photographs of the scales above mentioned, as well as of 

 Amphipleura pellucida and Surrirella gemma, taken and 

 presented by Dr. J. J. Woodward, were exhibited. 



Wednesday, April 19, 1871. 



Mr. Wm. H. Mies in the chair. Thirty-three persons present. 



Mr. F. W. Putnam made a verbal communication on the 

 classification of fishes, suggested by considerations on the 

 discovery of the so called Ceratodus, in Australia. 



Mr. Edwin Bicknell, of the Museum of Comparative 

 Zoology, said, a few months since, Prof. Agassiz handed him 

 a fossil tooth of the Ceratodus to have sections made from it. 

 On making the sections and submitting them to the micro- 

 scope, he had found the structure to correspond very closely 

 with such teeth of sharks as he had examined, and he con- 

 sidered any one to be perfectly warranted in referring the 

 fossil tooth to the shark family, although subsequent discov- 

 ery of the living fish shows it not to belong to it. Prof. 

 Agassiz has teeth of the recent fish, which will be subjected 

 to examination hereafter. 



Mr. Bicknell said he considered it unsafe to found genera, 

 or even species, upon the microscopical structure of a single 

 tooth or bone, although it has proved correct in many cases-. 

 Prof. Owen founded a genus of extinct reptiles (Labyrintho- 

 don) upon the structure of some fossil teeth. Prof. Jeffries 



