538 REPTILIA. 



towards the next succeeding it in the great scale of Nature, he will 



find himself insensibly led on by such gentle gradations that the 

 transition from any one class to another is almost imperceptible. 

 Nihil per saltum is one of the most obvious laws in Creation ; 

 and of this, perhaps, we could not select a more striking illustration 

 than is afforded by the Lepidosiren (Jig. 238). 



Two distinct species of this most remarkable animal have been 

 met with : one, the Lepidosiren paradoxa, discovered by Dr. Nat- 

 terer in the river Amazon ; the other, Lepidosiren annectans, was 

 found by T. C. B. Weir, Esq. and is a native of the African con- 

 tinent, inhabiting the river Gambia. An individual of the species 

 last mentioned has been minutely anatomized by Professor Owen,* 

 and both in its outward form and internal organization is so pre- 

 cisely intermediate between a Reptile and a Fish, that, while Dr. 

 Natterer regards it as an Amphibian, Professor Owen considers 

 that, notwithstanding that it possesses lungs, the icthyic characters 

 predominate, and it ought rather to be ranked among the Fishes. 



The body of the Lepidosiren annectans (Jig. 238) is about a foot 

 long, and covered with scales, resembling those of the cycloid fishes : 

 the tail gradually tapers to a point, but is fringed above and below 

 with a membranous fin, supported by numerous soft, elastic, trans- 

 parent rays, articulated to the superior and inferior spines of the 

 caudal vertebrae ; the gills are covered by opercula, not being 

 exposed, as in the proper Amphibia ; and, moreover, it has four 

 rudimentary fins, or legs, as the reader may choose to call them. 

 These rudimental extremities are round, filiform, and gradually 

 attenuated to an undivided point ; being supported internally by a 

 single-jointed soft or cartilaginous ray. The nostrils of the Lepi- 

 dosiren, however, are merely two blind sacs as in fishes, and do not 

 communicate with the mouth or fauces ; a character which Professor 

 Owen regards as the only decided evidence that the animal ought 

 in preference to be ranked among the class Pisces. 



* Transactions of the Linnean Society for 1840. 



