pectinirhomb

from The Century Dictionary.

• noun In the Echinodermata, one of the rhombic areas of parallel stereome folds on the outer surfaces of certain thecal plates in some cystideans. New areas overlap the edges of adjoining plates and often exhibit a suppression of the folds along their diagonals, which coincide with the suture-lines, resulting in a division of the individual areas. They are similar to the pore-rhombs. Also termed pectinated rhombs.