Notation question: like a direct product

[pellman]

I am coming across a notation in a math text whose form and context suggest it is something like a direct product. The symbol is a multiplication X with a vertical line connecting the two left side ends. Can someone identify this symbol please?

The context can be seen here http://books.google.com/books?id=3J...CQrZcB&sa=X&oi=book_result&ct=result&resnum=1 2/3rds the way down on the page. This is an online preview of the text I am reading.

 

[Hurkyl]

Maybe a semidirect product?

 

[pellman]

Hurkyl to the rescue again. That is it.

And look. The article lists the LaTex commands. $$G = R^4 \ltimes SL(2,C)$$