sirenidæ

from The Century Dictionary.

• noun In herpetology, a family of gradient or tailed amphibians, typified by the genus Siren, with external gills persistent throughout life, maxillaries absent, intermaxillaries and mandible toothless, palatines and pterygoids undeveloped, and orbitosphenoids large, anterior, and forming part of the palate.
• noun In ichthyology, a family of dipnoous fishes: same as Sirenoidei, and including Lepidosirenidæ and Ceratodontidæ.