46 



characters belonging to the Tnnicaies and Annclides, and unex- 

 pected relations are revealed between the Vertebrata and tlie 

 Invertehnda. 



The Most Highly Organised Fish. 



In the Leindosimi, the highest of all the fishes, we find 

 an organization of a no less conii:)lex natm-e. The genus was 

 founded in 1837 by Dr. Natterer for the reception of a singular 

 animal to which he gave the specific name of jxiradoxa, discovered 

 by him in America, inhabiting the swamps in the vicinity of the 

 liver Amazon. This species, which attains a length of three feet, 

 the l)ody l)eing eleven times as long as tlie head, * is now 

 becoming very rare. In 1839, Professor Owen referred specimens 

 from the river Gambia of West Africa to tlie same genus, under 

 the designation of Lepidimrai dimedens, and classed them in a 

 provisional group between the reptiles and fishes. They are 

 placed by Professor Huxley in the highest order of his classifica- 

 tion of fish, namely, tlie B'qjnoi or " double Ijreathers," and are 

 popularly known as the mud fishes. 



Th(!se paradoxical " scaled sirens " have Avell developed 

 reptilian lungs co-existing with functional internal branchia?, 

 and are capable of living either in the water or out of it. Their 

 structure and habits are very i)eculiar. During the rainy season, 

 the \vat<'rs of the Gambia overttow its banks, and the mud fish is 

 carried out of the true bed of the river. AVhen the waters retire 

 it is left stranded ; then, burrowing in the softened mud, it coils 

 itself up, keeps open a communication with the air above its nest, 

 and breathes liy means of its modified swimming bladder. It 

 thus remains inactive till the return of the fioods soften the walls 

 of its cell, when it emerges, and resumes its former habits. 

 They have been found in a semi-torpid state eighteen inches 

 below the surface, in situations were the ground is dry and hard 

 for months in the year, and are dug out by the natives with a 

 .sharp pointed stick and used for food. 



* Ti-anscactions of the Linnean Society. Vol. xviii. 



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