2 [January, 



destruction among fish, was the discoloration of the water of the bay, from a 

 marine green to a dirty milk-white hue, followed by a decided odor of the gas; 

 so much of it being present on many occasions as directly to blacken a clean piece 

 of silver, and to blacken paint work in a few hours. 



The fish, during this evolution, rose in vast numbers from the bottom; and after 

 struggling for sometime in convulsions upon the surface, died. 



I was particularly struck by this fact, that all of them during the time that they 

 were under its influence, acted in precisely the same manner. The first thing 

 noticeable with regard to its effect upon them, was that on coming near the surface, 

 they seemed to have much difficulty in remaining below it at all. They then 

 rose completely to the surface, struggling vainly to dive beneath. This was 

 followed by violent springing and darting in various directions evidently with- 

 out control of direction for they moved sideways, or upon the back, and some- 

 times tail first, with great velocity. After a little time their motion became 

 circular, and upon the back, the circle of gyration constantly diminishing, and the 

 rapidity of the motion as constantly increasing, until there was a sudden cessation 

 of all motion. The head then floated about the surface, the body being in a perpen- 

 dicular position. A few convulsive movements shortly followed, and they were 

 dead. 



I have watched thousands of them so dying ; and in every instance such was the 

 mode of death. Having taken them at the moment of death and immediately after, 

 a rude examination showed in all the same appearances. The intestines and brain 

 were gorged with blood, much darker than natural. The gills were almost black, and 

 the air-bladder ruptured. A premonitory symptom that such destruction was about 

 to occur, was the previous appearance of unaccountable numbers of fishing-birds, 

 especially of the Pelicans. On one occasion, taking the known size of the Island 

 of San Lorenzo as a guide for measurement, we concluded that there was a body 

 of Pelicans 5 miles long, one mile wide, and 300 feet thick, filling the water and 

 air as closely as possibly they could do. How many were there ? Can we wonder 

 at the size of guano deposits ?'' 



Dr. Leidy called the attention of the members to a fossil tooth and a 

 fragment of a second, from the collection made by Mr. Culbertson in 

 Nebraska Territory, which, he observed, belonged to a new species of 

 Rhinoceros, or probably Acerotherium. The former specimen is proba- 

 bly a third premolar, the latter a portion of the fourth. A great pecu- 

 liarity in the teeth is the confluence of the inner lobes with each other, 

 and their separation to the base from the outer lobes. They possess a 

 remarkably strong basal ridge, and indicate an animal larger than any 

 species of existing Rhinoceros : the greatest transverse diameter of the 

 third premolar being 2^ inches; its antero-posterior diameter If inches. 

 For the species the name Rhinoceros Americanus is proposed. 



Dr. Leidy also called the attention of thv9 members to the fine mounted 

 specimen of Polar Bear now in the Hall, the skin of which had been 

 lately presented by Dr. E. K. Kane, U. S. N. 



On motion of Dr, Fisher, the letter of Mr. Peale, read this evening, 

 was referred to the Library Committee, with power to act. 



Dr. Fisher announced that the collection of fossil foot-prints of Fishes, 

 belonging to Mr. Dexter Marsh, of Greenfield, Mass., was for sale. 



On motion of Mr. Moss, the suggestions contained in the Report of 

 the Librarian for 1851, were referred to the Library Committee. 



