Occasionally a strange, dead kit is produced by the female.

They may appear half-developed, deformed, or bizarrely misshapen.  Usually this is an indication of a near full-term embryo that had died in-utero and been partially reabsorbed before being expelled.

Here are some photos (the first two are courtesy of Wenda Barron -  www.granitecitychinchillas.co.uk )

There are many reasons for a foetus to die whilst in the womb - but thankfully it is relatively rare.  In 18 years I have only ever had two produced to different females.