The Galaxy Nexus mode does not support the “USB Mass Storage” , although other devices Android 4.0 Ice Cream Sandwich should support this feature. The explanation given by Dan Morrill , engineerAndroid , in a comment on an article to Reddit in which he stated that the Galaxy Nexu s does not support USB mass storage mode because there is no memory expansion slot. Morrill said that the devices with SD card slot will have this feature but the only devices that have no internal memory.
This thing could be a problem for users Mac and Linux platforms as these do not have native support for the standard Media Transfer Protocol (MTP) is used by the Galaxy Nexus and will then need to use applications like Android File Transfer to transfer files. No problem, however, for users of Windows.