1) Array 
(= actinotrichium (singular))
actinotrichia 1. Threadlike (hairlike) fibers in the finfolds of fish larvae that eventually develop into fin rays. 2. Slender, horny, flexible, unsegmented fibrils which strengthen the embryonic fin fold. Actinotrichia are translucent, exhibit birefringence (double refraction) and are composed of a scleroprotein called elastoidine.