1852.] 59 
April 20th. 
Vice-President Brincss in the Chair. 
Letters were read 
From Capt. 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 EK. India station. 
From the Royal Academy of Sciences of Brussels, dated January 10th, 
1850, and March 15th, 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 Girard ;” 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 ; 
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 Hippopotamidee,”’ 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. Inall, 
the penultimate vertebral plate is inverted V formed,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 : 
Testupo Nesrascensis, Leidy. 
Stylemys Nebrascensis, Pr. A. N.5., v. 173. 
TrEsTUDO HEMISPHERICA, Letdy. 
Emys hemispherica, ib. 
Testupo Owent, Leidy. 
Emys Owen, ib. 327. 
Testupo Cunsertsoni, Leidy. 
Emys Culbertson, 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 1-1750th to the 1-777th of 
an inch in diameter. 
