FAillLT, IX— STMBRANCHID^. 655 



Family, IX— SYMBRANCHID^. 



Gill-openings confluent into a single slit, which is situated on the abdominal surface. Gills well 

 developed or rudimentary. Body elongated. The humeral arch may or may not be attached to the skull. 

 Margin of the upper jaw formed by the premaxillaries, the maxillaries being internal and parallel to them. 

 Barbels absent. Palatine teeth, when present, in a single row or a narrow band. Vertical fins rudi- 

 mentary, in the form of mere folds of skin, and no paired ones. Scales, if present, minute. Vent far 

 behind the head. An accessory breathing sac present or absent. Air-vessel absent. Ribs present. Stomach 

 destitute of a blind sac. No pyloric appendages. Ovaries with oviducts. 



The Families SynibrancJudx and Murixnidre belong to the Phijsostomi apodes of some authors, and the 

 former tropical family is fairly represented in the continent of India, whereas the latter is more numerous in 

 the seas than in the fresh waters. 



Geographical distribution. — Fresh and brackish waters of tropical Asia and America ; also Western 

 Australia and Van Diemen's land. 



SYNOPSIS OF GENERA. 



First group — Amphipxina. 



Humeral arch not attached to the skull : an accessory breathing apparatus. Scales present. 



1. Amphipnous. Palatine teeth in a single row, p. 655. 



Second group— Stmbeanchina. 

 Humeral arch attached to the skull. No accessory breathing apparatus. Scales absent. 



2. Mojiopterus. Gills rudimentary, p. 656. 



3. Symbranchus. Gills well-developed, p. 657. 



First group — Amphipnina. 

 Humeral arch not attached to the skull. An accessory breathing apparatus. Scales present. 



Genus, I — Amphipnous. MiiUer. 



Pneum.ahranchus, McClelland. 



Branchiosfegals six. Gill membranes almost entirely grown to the isthmus, and having a single^ transverse 

 opening. Three branchial arches with the lamince rudimentary, divided by narrow slits. A respiratory air sac exists 

 on the neck behind the head communicating with the gill cavity. Palatine teeth in a single, welUdeveloped roiu. 

 Scales present and arranged in longitudinal rows. 



This amphibious fish, when kept in an aquarium, may be observed to constantly rise to the surface for 

 the purpose of respiring atmospheric air direct. It usually remains with its snout close to the surface and in 

 like manner lies in the grassy sides of ponds and stagnant pieces of water, so that without trouble it may 

 obtain its modicum of air. McClelland observed (Cal. Joum. Nat. Hist, v, p. 195). " I have had two live 

 Guchias by me now for a period of twelve months ; they are still as well as when I first obtained them, though 

 from an ignorance of their proper food, as well as a desire to know how long they are capable of existing 

 without any, they had nothing to eat during that period to within the last few months, when some small fish 

 and shrimps were put aUve into the vessel." 



In Amphipnous cucUa, we find " that of all the arches the second alone possesses laminre for the purposes 

 of breathing : and those consist merely of a few long fibrils attached to the middle of the arch and occupying 

 but a very small extent of its surface : the third supports in the place of laminas, a thick and semi-transparent 

 tissue, which in large individuals of the species possesses a fringed or denticulated appearance on its edge ; 

 whilst the third and fourth are bare, having only the membrane that fills up the space between the arches 

 reflected over them. The principal organs of respiration are two small bladders, which the animal has the 

 power of filling with air, immediately derived from the atmosphere. They are placed behind the head, one on 

 each side of the neck, above the superior or vertebral extremities of the branchial arches, and are covered over 

 by the common integnment, presenting externally when distended with air, two protuberances of a round 



shape They present, when separated from their surrounding attachments and inflated with air, 



thin, transparent, membranous parieties, resembling the posterior portions of the lungs of a serpent. . . . 



