Thanks, yes I see that in Device Storage, the card is "SD card". When I use ES File Explorer, and go to the root, I see both "extsdcard" and "sdcard" (along with "system" and a number of others). So while the micro-sd is referred to as 'sdcard' in some places, in the file system it is extsdcard.
I thought I read somewhere that the internal memory is just an sdcard -- hope it doesn't pop loose! That would be bad.