972 
April 27, 1912, with President Nelson in the chair. 
Three papers were presented: 
Are Rabbits Rodents? J. W. GiwLEY. (To appear 
in SCIENCE shortly.) 
Remarks on the Skeleton of the Dinosaur, Stego- 
saurus: C. W. GILMORE. 
The type specimen of Stegosaurus stenops Marsh 
in the U. S. National Museum is the most com- 
plete skeleton of the genus that has yet been dis- 
covered, and the recent assembling of the large 
blocks of sandstone which contain this fossil 
enabled Mr. Gilmore to discuss several points in 
its anatomy. Especially attention was given to 
the position and arrangement of the elements 
which comprise the dermal armor, and since this 
is the only individual known which gives anything 
like a true idea of the manner in which the armor 
was attached the importance of the specimen is 
at once apparent. 
It was pointed out that there was a great di- 
versity of opinion among vertebrate paleontolo- 
gists, especially regarding the number and arrange- 
ment of the plates and spines constituting the exo- 
skeleton. Marsh in 1891 made the first pictorial 
restoration of Stegosaurus and placed the series of 
flat plates (12 in number) in a single row along 
the median line of the neck, back and tail, with 
four pairs of spike-like spines near the end of the 
tail. Iucas in 1901 published the next restoration, 
and was the first to show the plates (28 in num- 
ber) arranged in pairs. Later in a statement pre- 
pared under his direction the plates of .opposite 
rows (22 in number) were made to alternate, and 
the spines were reduced from four to two pairs. 
The latest conception, as exemplified by a recently 
mounted skeleton in the Peabody Museum of Yale 
University, shows a return to the paired arrange- 
ment of the plates (28 in number) and the reten- 
tion of four pairs of spines. 
It was shown that specimens in the National 
Museum corroborated most conclusively Lucas’s 
second interpretation, and with the exception of 
one or two points is entirely in accord with the 
evidence. 
That the plates of opposite rows did alternate is 
shown by the way they lay embedded in the rock, 
and that no two of them were precisely similar in 
shape or dimensions. 
It was demonstrated that the usual number of 
spike-like spines is two pairs, as shown by seven 
individuals, six of which are in the National 
Museum. 
SCIENCE 
[N.S. Vou. XXXV. No. 912 
The facts relating to the dermal armor which 
now appear to be established from this preliminary 
study are: 
1. That the armor of the neck, back and tail was 
found by two rows of erect plates, the elements of 
one row alternating with those of the other. 
2. That the total number of plates in the two 
rows was not less than 22. 
3. That the position of the largest plate of the 
series appears to be above the base of the tail, and 
not over the pelvis. 
4. That the usual number of dermal spines on 
the tail is 4, arranged in two pairs. 
Early Bird Migration in a Late Spring at Wash- 
ington, D. C., 1912: WELLS W. Cooke. 
The winter of 1911-12 was the coldest at Wash- 
ington, D. C., for many years, and yet several 
species, notably the robin, were more common than 
usual, due to unusually warm weather in De- 
cember. 
January, February and March to the 27th were 
far below the normal, and yet about half of the 
species of birds that arrived during this period 
were earlier than their average date. When, how- 
ever, these species were examined more carefully, 
it was found that those who arrived early were all 
species that occasionally winter as far north as 
Washington, and these early migrants undoubtedly 
represent individuals that had spent the winter in 
the heavily forested swamps and had been observed 
when they returned to open country. 
The rest of the species that arrived late during 
this cold period were all birds that winter far to 
the south of Washington. 
On March 28 the weather turned warm and re- 
mained above normal for a whole month. Imme- 
diately birds began to arrive from the far south 
that were decidedly ahead of their normal date, 
and in the case of some of them, earlier than the 
earliest previous date. This is one of the best 
examples of what usually happens when a cold 
spell begins to break. The cold had been wide- 
spread, holding the birds far south, and when the 
warm spell began the birds rushed north and 
continued their flight longer than usual until they 
were actually ahead of their schedule time. 
Almost every species for the whole of the rest of 
the migratory season of 1912 at Washington, D. C., 
arrived earlier than their average dates. 
M. W. Lyon, JR., 
Recording Secretary, pro tem. 
WASHINGTON, D. C. 
