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lonyx ; a terminal phalanx of a young animal of the same 

 species ; the right half of the lower jaw of a Beaver ; a por- 

 tion of the lower jaw of Castoroides Ohioensis, and a young 

 Mastodon tooth. 



He pointed out the peculiarities of the claw and tooth of the 

 Megalonyx. The claw much resembles that of the feline Car- 

 nivora, but is distinguished from it by the position of the tubercle 

 at its base. In the Megalonyx, which is one of the Edentata, 

 the tubercle is placed at the upper side of the base, operating to 

 give a lever power to the muscles of extension ; in the Carniv- 

 ora the tubercle is at the lower side, giving a similar power to 

 the muscles of flexion. 



The tooth of the Megalonyx is not encrusted with enamel, 

 has an elliptical crown, and a projecting ridge on the side which 

 distinguishes it from all the other Edentata of this continent. 



The fragment of the jaw of the Beaver did not materially dif- 

 fer from that of the existing species. 



The fragment of the jaw of the Castoroides was interesting as 

 belonging to the largest rodent known. A notice of the geolog- 

 ical position of this species by James Hall, and a description of 

 the cranium by Prof. Jeffries Wyman, were published in the 

 Journal of this Society, Vol. V. p. 385. The fragment now 

 exhibited belonged to a larger specimen than that from which 

 the description was taken. 



Dr. Durkee exhibited under the microscope specimens 

 of Polysiphonia formosa and Rhodomenia, from New Bruns- 

 wick ; also a solution of gelatin derived from Chondrus 

 crispus. 



The President presented a number of the bones which 

 had been missing from the anterior extremities of the Ma- 

 natus presented by him to the Society some time since. 



Mr. Belknap presented in behalf of Mr. George E. Tyler 

 a specimen of Agama from the plains of Sacramento, Cali- 

 fornia ; an unknown animal from the Bay of San Fran- 

 cisco ; and a Crawfish from the Isthmus of Panama. The 

 thanks of the Society were voted for the donation. 



