36 R. W. SHUFELDT, 
not quite reach the costal border of the sternum. The ultimate pair 
of pelvic ribs, noted in the museum skeleton above, are absent here. 
Passing to another skeleton of Dendrocygna autumnalis of the 
ARMSTRoNG series (453), a female, I find seven facets on both the 
costal borders of the sternum, with two of the three pairs of 
pelvic ribs having haemapophyses that reach the sternum for 
articulation. The last pair, while they possess long, delicate, sweeping 
haemapophyses, they do not, upon either side, reach the costal 
sternal border. 
In this skeleton, four of the dorsal vertebrae possess 
haemal spines, the last one being thoroughly developed and 
4 or 5 mm, long. Thus, in this skeleton, it is only the last dorsal 
vertebra that lacks a haemal spine; while in the museum specimen 
(No. 1491) and 454 described above, the last two dorsal vertebrae 
are entirely devoid of haemal spines. 
In another skeleton of Dendrocygna autumnalis, a male, of the 
ARMSTRONG series (455), there are seven facets on each of the 
sternal costal borders; two pair ofthe pelvic ribs articulate with 
the sternum through costal ribs; the haemapophyses of the third 
pair of pelvic ribs are long and sweeping, but do not reach the 
sternum; finally, the leading four dorsal vertebrae have well devel- 
oped haemal spines, while the fifth or last one has none. 
Such variations as these are interesting, and I have found them 
present in many other species of birds. They may occur in all 
vertebrates up to man, in whom I have found not only a pair of 
lumbar ribs, but a pair of well developed ribs on the seventh cervical 
vertebra. 
As to the ribs themselves in Dendrocygna, they present nothing 
especially peculiar, although they have, to be sure, characters of 
their own, which, although perhaps insignificant, still pertain strietly 
to this genus of ducks, and are different, character for character, 
from what we find in other species. These ribs are somewhat broad, 
considerably compressed from side to side, and, together with the 
last pair of free, cervical ribs, all support rather large epipleural 
appendages. The epipleurals of the last pair may be very small 
(454), or nearly as large as the others (455). 
Both the morphological characters of the ribs and the characters 
of the vertrebrae in Dendrocygna differ very widely from the corre- 
sponding ones in any particular rib or vertebra in such forms as 
Harelda hyemalis, Polystieta stelleri, Hymenolaemus, or any of the 
