lep·to·ceph·a·lus 
(lĕp′tə-sĕfə-ləs)
(lĕp′tə-sĕfə-ləs)n. pl. lep·to·ceph·a·li (-lī′)
The small, laterally compressed, transparent larva of an eel or of any of certain related fishes, such as a tarpon.
[New Latin : LEPTO- + cephalus, head (from Greek -kephalos, -headed); see -CEPHALOUS.]