If I’m not mistaken, the picture Stylites posted is the folded cappa magna. Certain prelates such as canons to whom the cappa has been granted by indult are privileged to wear a cappa magna but never to let down its train except at the Adoration of the Cross on Good Friday, while others such as bishops are privileged to let down the train in some circumstances (where they exercise ordinary authority) but not others (only a cardinal may let down the train of the cappa magna in the presence of the pope). When not let down, the train must be folded and tied up on the left side. Properly done, it looks like the picture below, and is sometimes informally called a cappa parva.
It is admittedly a little difficult to make out exactly what is going on in that picture; if it’s true that there are arm-holes, that is incorrect practice but a common enough abuse. I
think that what we are seeing on his left-hand side there is the rolled-up portion.
And if it’s not a folded cappa magna, then it is the mantellone (which is
not the mantelletta), although why it looks rolled up at the bottom I couldn’t say.
http://books.google.com/books?id=FA...9ylv6biZy5wdq1yv6Q&ci=125,216,800,1259&edge=0