1852.] 59 



^pril 20th. 

 Vice-President Bridges in the Chair. 



Letters were read 



From Cap^,t. Wm. McCluney, U. S. N., addressed to Dr. Ruschenber- 

 ger, dated New York Navy Yard, April 17th, 1852, offering to further 

 the objects of the Academy, during the cruise of the U. S. Squadron on 

 the E. India station. 



From the Royal Academy of Sciences of Brussels, dated January 10th, 

 1850, and March 13th, 1851, acknowledging the receipt of the Journal 

 Part 4, Vol. 1, and Part 1, Vol. 2. 



Dr. Leidy read a paper entitled '^ Characteristics of some new Rep- 

 tiles in the Museum of the Smithsonian Institution, by Spencer F. 

 Baird and Charles Grirard;" which, being intended for publication in 

 the Proceedings, was referred to a Committee consisting of Dr. Hal- 

 lowell. Dr. LeConte and Dr. Leidy. 



Dr. Leidy also presented a paper from Prof. Dana, being a continu- 

 ation of his descriptions of the Crustacea of the Exploring Expedition 3 

 which was referred to the original Committee. 



Dr. Leidy read also a paper ^'On the Osteology of the Head of the Hip- 

 popotamus and a Description of the Osteological Characters of a New 

 Genus of Hippopotamidse," which being intended for publication in the 

 Journal, was referred to Dr. Ruschenberger, Dr. Woodhouse and Dr. 

 Hallowell. 



Dr. Leidy stated that he had been studying the characters of the fossil tortoises 

 from Nebraska Territory, and had come to the conclusion that they had been 

 terrestrial and not aquatic in their habits,and belonged to the genus Testudo. In all, 

 the penultimate vertebral plate is inverted Vformed,enclosing with the pygal plate 

 the last vertebral plate ; the costal plates are alternately broad and narrow ; and 

 in those specimens in which the marks of the pygal scute remains, it is undivided, 

 as in the recent Testudo. The names of those species described recently should 

 be changed as follows : 



Testudo Nebrascensis, Leidy. 



Stylemys Nebrascensis, Pr. A. N. S., v. 173. 

 Testudo hemispherica, Leidy. 



Emys hemispherica, ib. 

 Testudo Oweni, Leidy. 



Emys Oweni, ib. 327. 

 Testudo Culbertsonii, Leidy, 



Emys Culbertsonii, ib. vi. 34. 



Dr. L. also called the attention of the members to a specimen of " Red Snow " 

 Protococcus nivalis, beneath the microscope, which was brought by Dr. E. K. 

 Kane, U. S. N., from the Arctic region. It consists of simple, spherical vesi- 

 cles, with a transparent, colorless, shining cell wall, and bright red, granular 

 contents. The vesicles or cells measure from the i-1750th to the l-777th of 

 an inch in diameter. 



9 



