121 



100. Surirella, striatula. 107. Pleurosigma strigosum. 



101. " two n. s. 108. " strigilis. 



102. " lata. 109. " hippocampus. 



103. Campylodiscus cribosus, AV.S. 110. Pinnularla peregrina. 



= C. argus, Bail. 111. Stauroneis aspera =S. pul- 



104. " parvulus. cliella, W. S. 



105. Doryphoria Boeckii. 112. Actinoptychus senarius. 



106. Pleurosigma Balticum. 113. Amphipleura sigmoidea. 



Undetermined species of Ampliiprora, Navicula, Pinnularia, Am- 

 phora, Surirella, and Cossinodiscus. 



The President made a communication on the mode of 

 formation of the rattle of the rattlesnake. 



In a fcetal specimen examined, the scales cease toward the end of 

 the tail, and the unsealed portion is covered by thickened cuticle, the 

 rudiment of a rattle, which must faU off; as the animal grows, the 

 last three vertebrae are covered with hardened cuticle arranged in 

 ridges ; as growth continues this covering is displaced, a new layer 

 forming underneath it, and the old slipped backward over one ridge 

 in a manner not well determined ; this is in turn displaced by a new 

 layer beneath, pushed backward over a single ridge, and so on indefi- 

 nitely. An interesting point yet to be settled is whether the cuticular 

 caudal rings are set free at the time of moulting. That there is no 

 definite relation between the age of the animal and the number of 

 rattles, he said, was shown by specimens over six feet long having 

 only two rattles, and others of eighteen inches with six or seven. 



Dr. White announced a very extensive and valuable dona- 

 tion of skins and skulls of Xorth American mammals by the 

 Smithsonian Institution, and mostly of rare animals from 

 the little-explored regions of the western and southwestern 

 territories, known only to naturalists Avithin a few years. 

 Among tlie skins were those of the grizzly bear, wolf, fox, 

 lynx, mink, skunk, badger, otter, raccoon, weasel, squirrels, 

 spermophiles, woodcliuck, beaver, muskrat, porcupine, hares, 

 deer, and prong-horned antelope ; many of them in excellent 

 condition for mounting, and making complete many of the 

 series in the Society's cabinet. In a larger building these will 

 make a 'very striking and instructive addition to its museum. 

 Among the skulls are those of the grizzly bear, wolf. Rocky 

 Mountain sheep, western deer, prong-horned antelope, lynx, 

 and marten, with horns of the antelope. Tlie thanks of 

 the Society were voted for this donation. 



