WD not mounting on Mac after improper ejection

WD External Drives External Drives for Mac
4

Screen Shot 2014-09-05 at 9.59.04 AM.png
Screen Shot 2014-09-05 at 9.59.04 AM.png1087×682 77.3 KB

My Passport Ultra will not mount. How can I fix this? Can anyone help?

Best,

Tim