What is Growing on this Devonian Brachiopod?

The following pictures are of a Middle Devonian Period brachiopod Mucrospirifer? found in Clark County, Indiana. It was found in Sellersburg (North Vernon) Limestone. What I am not sure about is little line segments creeping up the valve. Is it some sort of coral or algae?

This brachiopod will be cleaned next time I am at the workshop. It should hopefully reveal more details on this brachiopod.

UPDATE (05/26/2010): I think I figured out what this is.  After reviewing a KYANA Geological Society website Devonian Fossil section for an identification of a bryozoan growing on a horn coral I found pictures of the Hederella sp encrusting an Orthospirifer fornacula. It too is found in the North Vernon Formation of Clark County, Indiana of the Middle Devonian Period.  Thanks to Alan G. for providing the original images for the KYANA post!

Learn more about hederellids or hederelloids on Wikipedia.