426 MANUAL OF ZOOLOGY. 



affected by this. Lastly, sometimes, at any rate, there are 

 rudimentary external branchiae placed on the side of the neck. 

 This feature, as will be seen shortly, is characteristic of all the 

 Amphibians, either permanently or in their immature state. 



Upon the whole, then, whilst for the purposes of systematic 

 classification the Lepidosiren must be placed amongst the Fishes, 

 it is not to be forgotten that many of its characters are those 

 of a higher class, and that it may justly be looked upon as a 

 connecting link, or transitional form, between the two great 

 divisions of the Fishes and the Amphibians. 



As regards their distribution and mode of life, two species 

 at least of Lepidosiren are known the L. paradoxa from the 

 Amazon, and the L. annectens from the Gambia. They both 

 inhabit the waters of marshy tracts, and appear to be able in 

 the dry season to bury themselves in the mud, forming a kind 

 of chamber, in which they remain dormant till the return of the 

 rains. Recently there has been discovered in the rivers of 

 Queensland (Australia) a fish which has been described under 

 the name of Ceratodus (?) Fosteri, and which would appear to 

 be very closely related to the Lepidosiren. This singular fish 

 the "Barramunda" of the natives is from three to six feet 

 long, and has the body covered with large cycloid scales. The 

 skeleton is notochordal, all the bones remaining permanently 

 cartilaginous. There is a well-developed operculum, but as 

 in Lepidosiren no branchiostegal rays. The tail is homocercal, 

 and the pectoral and ventral fins are supported by a median, 

 many-jointed, cartilaginous rod, with numerous lateral branches 

 on each side. The heart consists of a single auricle and 

 ventricle, with a " Ganoid " bulbus arteriosus. There are five 

 branchial arches, of the Teleostean type, but cartilaginous. 

 The swim-bladder is single, composed of two symmetrical 

 halves, cellular in structure, with a pneumatic duct and glottis, 

 as in Lepidosiren. The intestine has a spiral valve, and there 

 are no pyloric caeca. 



Upon the whole, Dr Giinther concludes that the Dipnoi are 

 to be regarded as a simple sub-order of Ganoids, and that the 

 entire order Ganoidei may be united with the Elasmobranchii 

 into a single order, called Palceichthyes, characterised by having 

 a "heart with a contractile bulbus arteriosus, intestine with a 

 spiral valve, and optic nerves non-decussating." 



