298 ZAGLOSSUS. 
The first and second support each a single pair of ribs, while the third supports 
the fifth and sixth pairs. This last piece thus evidently represents two sternebra 
fused, as indicated in addition, by a slight furrow on the sternebrum between 
the last two sternal ribs, marking the point of fusion. There are four remain- 
ing sternebra making nine in all, but these last are small and do not support 
ribs. In an old individual the five rib-bearing sternebra are reduced to three, 
owing to the complete fusion of the last three. Gervais’s figures indicate 
similar conditions. The dorsal end of the sixth sternal rib is greatly expanded, 
and so likewise are the ventral segments of ribs 7 to 12, which overlap each the 
one next anterior. Ribs 13 and 14 have a cartilaginous connection only, with 
these bony plate-like portions, while ribs 15 and 16 are short, and backwardly 
directed, without particular connection with the thoracic basket. 
GIRDLES AND LimMBps.— The characters of the pelvic and pubic girdles are 
in general similar to those of the Echidna as ably discussed by Gregory (1910, 
p. 152-153). The various elements of each are in adults thoroughly fused, 
although the line of union of the scapula with the interclavicle usually 
remains distinct. In M. C. Z. 12,414, an old animal, the line of suture is still 
clear between the left coracoid and procoracoid. 
There can be no doubt that the Proechidna with normally three claws on 
each foot is a derivative from some form which like the Echidna was five-clawed. 
In this and certain other respects, it therefore represents a stage in advance of 
the condition shown by the Echidna so that as Toldt (1905) justly says, the term 
Proechidna is somewhat of a misnomer. Several cases are on record in which 
more than three claws have been noted on the foot of the Proechidna, and these 
must undoubtedly be considered as instances of regressive variation. On both 
fore and hind feet it is digits 2, 3, and 4 that are normally provided with claws. 
Digits 1 and 5 are usually covered by a callosity and at most are mere promi- 
nences in external aspect. Of the eight specimens in the collection of the Mu- 
seum of Comparative Zoédlogy, two only show more than the normal three claws 
on each foot. The first isamounted specimen, 6,722, from northern New Guinea, 
in which there is a claw on digit 5 measuring about 19 mm. in both right and 
left fore feet. I suspect that there were also claws on digit 5 of each hind foot, 
but these if present must have become lost. The chief reason for this belief 
is that they exist on the fifth digits of the fore and hind feet in the United States 
national museum’s specimen 22,992 which is the skeleton of apparently the 
same individual whose mounted skin is in the Museum of Comparative Zoél- 
ogy. Both were purchased independently from Ward’s Natural science estab- 
