In some other respects they resemble the lower _Ostariophysi_, especially the electric eel and the eel-like catfishes. But these resemblances, mainly superficial, may be wholly deceptive; we have no links which certainly connect the most fish-like Apodes with any of the other orders. Probably Woodward's suggestion that they may form a series parallel with the _Isospondyli_ and independently descended from Tertiary Ganoids deserves serious consideration. Perhaps the most satisfactory arrangement of these fishes will be to regard them as constituting four distinct orders for which we may use the names _Symbranchia_ (including _Ichthyocephali_ and _Holostomi_), _Apodes_ (including _Enchelycephali_ and _Colocephali_), _Carencheli_, and _Lyomeri_. =Order Symbranchia.=—The _Symbranchia_ are distinguished by the development of the ordinary fish mouth, the maxillary and premaxillary being well developed. The gill-openings are very small, and usually confluent below. These fresh-water forms of the tropics, however eel-like in form, may have no real affinity with the true eels. In any event, they should not be placed in the same order with the latter. The eels of the suborder _Ichthyocephali_ (ιχθύς, fish; κεφαλή, head) have the head distinctly fish-like. The maxillary, premaxillary, and palatines are well developed, and the shoulder-girdle is joined by a post-temporal to the skull. The body is distinctly eel-like, the tail being very short and the fins inconspicuous. The number of vertebræ is unusually large. The order contains the single family _Monopteridæ_, the rice-field eels, one species, _Monopterus albus_, being excessively common in pools and ditches from China and southern Japan to India. The eels of the suborder _Holostomi_ (ὀλός, complete; στόμα, mouth) differ from these mainly in the separation of the shoulder-girdle from the skull, a step in the direction of the true eels. The _Symbranchidæ_ are very close to the _Monopteridæ_ in external appearance, small, dusky, eel-like inhabitants of sluggish ponds and rivers of tropical America and the East Indies. The gill-openings are confluent under the throat. _Symbranchus marmoratus_ ranges northward as far as Vera Cruz, having much the habit of the rice-field eel of Japan and China. The _Amphipnoidæ_, with peculiar respiratory structures, abound in India. _Amphipnous cuchia_, according to Günther, has but three gill-arches, with rudimentary lamina and very narrow slits. To supplement this insufficient branchial apparatus, a lung-like sac is developed on each side of the body behind the head, opening between the hyoid and the first branchial arch. The interior of the sac is abundantly provided with blood-vessels, the arterial coming from the branchial arch, whilst those issuing from it unite to form the aorta. _Amphipnous_ has rudimentary scales. The other _Holostomi_ and _Ichthyocephali_ are naked and all lack the pectoral fin.