SUB-FAM. 1. HEMIPHRACTINAE.–Teeth are carried by both jaws, the vomers and the palatine bones; or by the palatines and parasphenoids in _Amphodus_. The vertebrae are opisthocoelous, devoid of ribs, and the sacral diapophyses are not dilated. The shoulder-girdle and sternum are strictly arciferous. The omosternum is very much reduced; the metasternum forms a cartilaginous plate. The tongue is slightly free behind. The tympanum is distinct. Three genera, with eight species, all inhabitants of South America. _Hemiphractus._–The head is large; the upper surface of all the cranial bones appears pitted, owing to most of the covering skin being involved in the ossification. The temporal fossa is bridged over or roofed in by the fronto-parietal and the squamosals, so that the orbit is completely encircled by bone, as in _Pelobates cultripes_. The terminal phalanges are simple and are not dilated into discs. The teeth of the lower jaw are {211}very small and numerous. The tongue is round and very small. _H. scutatus_, the only species, living in Ecuador and Colombia, is a frog-like creature, with a large helmet-shaped head. Total length 2½ inches. _Ceratohyla_ has the same kind of helmet-shaped head, and the orbit is likewise enclosed by bone, but the terminal phalanges are claw-shaped and carry regular adhesive discs. This genus, the five species of which live in Ecuador, bears undoubted resemblances to the Hylidae. In _C. proboscidea_ the upper eyelid is produced into a little upright fold, as in _Amphignathodon_ and some species of _Nototrema_ and _Ceratophrys_ among Cystignathidae. The snout is produced into a long, compressed, bifid appendage, and the heel carries a triangular flap. In _C. bubalus_ the partly ossified helmet sends out a pair of diverging processes, formed by the squamosals, extending backwards and sideways from the concave and ridged interorbital spaces. The tip of the snout and the tips of the divergent horns form an equilateral triangle, and the whole head bears a striking resemblance to some of the fossil Reptiles from the Elgin Sandstone, e.g. _Triceratops_. Total length 3 inches. _Amphodus wucheri._–The only species of this genus has been found near Bahia. It has teeth on the palatine bones and five series of small teeth on the parasphenoid, but none on the vomers. The teeth of the mandible number about eleven on each side and decrease in size towards the symphysis. The tympanum is distinct; the heart-shaped tongue is free behind. The cranial bones are only slightly pitted. The skin is smooth above, chocolate-brown, spotted with yellow, and with a yellow band on the sides of the body beginning with the upper eyelid and ending in a broad patch above the vent. The under parts are yellowish white. SUB-FAM. 2. CYSTIGNATHINAE.–The upper jaw alone is provided with teeth. Vertebrae procoelous. The twenty-seven genera of this sub-family have been arranged in the following key, merely for convenient determination.