218 



plete state of solidity, and that this pressure has produced such 

 a structural arrangement as to develop particular planes of cleav- 

 age where the adhesion was the slightest. This supposition has 

 been sustained by experiment, recently instituted in England, in 

 which it has been demonstrated that scales of mica and other 

 material of flattened form, intermingled with plastic clay and sub- 

 mitted to continuous and energetic pressure, assume approximate 

 parallelism, and impart to the mass a laminar structure. Where 

 cleavage shows itself in limestone containing mica scales and 

 flattened particles of silica, the microscope has detected an ap- 

 proximate degree of parallelism between these substances and 

 the cleavage planes. 



Dr. S. Ivneeland, Jr., exhibited two specimens of Siredon, 

 taken in Portage Lake, Michigan, which were described by him 

 in the Proceedings of February, 1857, and which he had suc- 

 ceeded in keeping alive. These animals are very hardy, the 

 water in which they were contained having been frozen and 

 thawed many times in succession during the last winter, when 

 their only food was such minute matter as they might have found 

 in the lake water. They have maxillary and palatal teetli, and 

 though they are very much feared by the Indians, on account of 

 the supposed poisonous nature of their bite, yet Dr. Kneeland 

 has not known them to attack each other ; and he himself handles 

 them very freely, without any attempt of the animal to bite. 

 The heads of the two specimens are of different shape, and 

 possibly they are of different sexes. Since they have been in 

 Boston, they have been fed upon live worms by Dr. Durkee, of 

 which they will consume several every day. Near the gills 

 upon the surface of the body are a number of parasitic worms, 

 rough dx'awings of which were exhibited by Dr. Durkee. 



Dr. H. R. Storer said he had been informed that an 

 Albino of the Common Striped Squirrel of Massachu- 

 setts {Sciurus striatus) had been taken at South Fram- 

 ingham. It was perfectly white, with pink eyes, and a 

 note like that of the common striped squirrel. 



The Secretary, at the request of Dr. T. M. Brewer, 



