1872.} 175 [Annual Report. 
suspending wire ropes, and by introducing small wedges be- 
tween the bodies of the vertebrae in those places where the 
curve should be most marked. The highest point reached 
by any of the spinous processes is at the posterior end. of 
the dorsal region. The flippers are presented of the natural 
size, each bone standing apart from the others at, or near as 
possible, the proper distance. They are attached to the scap- 
ule, and these to the ribs, but the chief support is obtained 
by two strong wires which pass from the back of the skull 
to the anterior loop, holding up a transverse rod passed 
through the head of each humerus. The advantage of this 
is evident, for any sinking of this rod will tend to strengthen 
_ the skeleton by pulling the ends nearer together. 
Some additions have been made to the homological series 
and several skeletons prepared and put aside to be mounted 
as soon as possible. 
Among the donations received this year two deserve spec- 
ial mention. One is a beautiful head of a walrus, obtained by 
Capt. Fish, presented through J. 8. Fay, Esq.; the other, the 
skeleton of an alligator, said to be about twelve feet long, 
shot in Florida and presented by H. 8. Greenough, Esq. 
RADIATA AND CRUSTACEA. 
Work on the Hydroids and Corals has been in progress 
during the winter, and the preliminary arrangements for the 
removal of the two classes nearly completed by the Custodian. . 
MOLLUSKS. 
Dr. P. P. Carpenter worked upon the labelling, arrangement 
and mounting of the shells for seven weeks and two days; 
the last tliree weeks of this time he was constantly occupied 
from 5.15 A.M.to 9.30 P.M. He was accompanied by an 
assistant, who cleaned and mounted the specimens under his 
direction. 
A large quantity of material which had accumulated was 
first unpacked and distributed into genera. The Bivalves 
