in the Museum of Buenos Ayres. 95° 
iliac bone ; those of the back part are placed longitudinally, and 
parallel to the median crest of the os sacrum, belonging to the - 
ischial bone of the pelvis, and rising towards the place to which 
are joined the lateral prolongations of the last sacral vertebra. 
The two posterior ale are distant from each other, but the 
anterior ones unite in the centre of the animal, and, with the 
high crest of the first three vertebre of the os sacrum, form 
a cross below the centre of the posterior and heaviest part of 
the shell. The iliac bone descending from this spot inclines 
a little inferiorly, forming at its lower end the articulation for 
the thigh termed the acetabulum, into which enters the hemi- 
spherical head of the femur. The direction of that part of the 
principal posterior ramus of the pelvis, termed the ischium, runs 
almost horizontally towards the place of the posterior ascending 
ala, which is a subcylindrical and very thick bone, extending 
inferiorly into a long perpendicular and slightly inclined plate. 
The os pubis, on the contrary, is very slender, similar to a small 
rod, which extends a little at the lower end, unites with the 
ischium, and forms a symphysis pubis, which until now was not 
known in the Glyptodon, as it is absent in all the pelves dis- 
covered. For this reason, we must calculate that it was very 
slender and delicate, being perhaps a little open in the centre, 
and merely united by cartilaginous substance, which is also the 
ease with the Peludos and with the Matacos of the present 
day. 
We perceive behind the pelvis the vertebral column of the 
tail, which is rather strong and composed of loose vertebra of 
different number in different species. Hach vertebra possesses 
a thick cylindrical part below, and a vertebral arch above, from 
which issue three perpendicular prolongations anteriorly and one 
horizontal one, with two obtuse points posteriorly. Of these 
the central one is the spinous process, and the other four the 
oblique processes. There issues from each side of the body of 
the vertebra, and between these processes, a transverse process 
with an elevation at its extremity. All these parts gradually 
diminish in a posterior direction, the last vertebra being a conical 
body without any arch or process on its surface. Generally the 
three vertebre at the base of the tail are not only the largest, 
but also differ by their more extended transverse processes; in 
the following ones this process is shorter, and at the end more 
reclinate, because it is these vertebrze which are connected with 
the caudal rings, and the three basal ones are not. 
I am only able to state with exactitude the number of the cau- 
dal vertebrae of G. spinicaudus ; they are ten, of which six are 
met with in the caudal rings. According to ‘the specimens ex- 
hibited in the Museum, we can calculate with exactitude that 
