Greg wrote:
In the next one around the middle of the photo the spider features are on the edge of a smoother area which may be of lower elevation. This smooth area seems inhospitable for some reason excep for a few branches.

http://barsoom.msss.com/moc_gallery/m13_m18/images/M14/M1401682.html

Alex writes:
Now this is a really cool image that I hadn't seen previously. In addition to the areas you note where the "spiders" appear to be part of the regional surficial erosional process(es), the part that is really interesting to me is where the swath crosses the rim of the impact crater, where I see dendritic/arboreal erosional features AT THE SURFACE with transport channels moving downgradient from the adjacent upland plateau (merging with polygonal terrain) to the crater rim.

Alex R. Blackwell
University of Hawaii