﻿210 Miss Agnes Crane — On Certain Living and Fossil Fishes. 



resemblance between the enlarged pbrangeal sac of Ampliioxus and 

 that of the tunicated raollusks or sea squirts. He considered the 

 lancelet also as allied to the annulosa, from the simple organization 

 of its respiratory and circulatory system, and M, Kowalevsky has 

 more recently traced a close affinity between this species and the 

 early stages of some Ascidians. Thus, in AmpMoxus are united 

 characters belonging to the Tunicates and Annelides, and unexpected 

 relations are revealed between the Vertebrata and the Invertehrata. 



The Most Highly Organized Fish. — In the Lepidosiren, the 

 highest of all the fishes, we find an organization of a no less complex 

 nature. The genus was founded in 1837 by Dr. Natterer for the re- 

 ception of a singular animal to which he gave the specific name of 

 paradoxa, discovered by him in America, inhabiting the swamps in the 

 vicinity of the river Amazon. This species, which attains a length 

 of three feet, the body being eleven times as long as the head,^ is now 

 becoming very rare. In 1839 Prof. Owen referred specimens from the 

 river Gambia of West Africa to the same genus, under the designation 

 of Lepidosiren aimectens, and classed them in a provisional group 

 between the reptiles and fishes. They are placed by Prof. Huxley 

 in the highest order of his classification of fishes, namely, the Dipnoi 

 or "double breathers," and are popularly known as '•'mud-fish." 

 These paradoxical " scaled sirens " have well-developed reptilian 

 lungs co-existing with functional internal branchiae, and are capable 

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

 habits are very })eculiar. During the rainy season, the waters of the 

 Gambia overflow its banks, and the mud-fish is carried out of the 

 true bed of the river. When 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 by means of 

 its modified swimming bladder. It thus remains inactive till the 

 return of the floods 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 where 

 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.^ The 

 body of the Lepidosiren is fish-like, and covered with small cycloid 

 scales, simply constructed pectoral and ventral limbs are present, 

 with a dorso-caudal fin. The notochord is persistent, but the skull 

 is partly bony, jDartly cartilaginous, and the costal arches and 

 neural and haemal spines are well ossified ; thus it forms a link 



^ Trans, of the Linnsean Society, vol. xviii. 



^ A specimen of Z. annectens has been on exhibition in the entrance hall of the 

 Brighton Aquarium for more than two years. It is kept at a regular temperature 

 of 70°, and is in a very thriving condition, having grown several inches since it has 

 been in the institution, and thickened proportionately. The animal generally lies 

 quietly at tlie bottom of its tank, rising occasionally to the surface to take in air. 

 It is fed three times weekly on small pieces of raw beef, which it can be observed to 

 eat in a very unusual manner. When the food is thrown in, the mud-fish stretches 

 itself leisurely and seizes it, as it comes within reach, between its sharply formed 

 vomerine teeth. After masticating it slowly, it throws it out with a quick jerk, and, 

 commencing at the other end, repeats the manoeuvre ; it then again rejects it, and 

 subjects it to a third process of mastication before finally swallowing it. 



