Prof. Owen's Description of the Lepidosiren annectens. 353 



be confessed that the physiological consequences of the modifications of the 

 nasal cavity above alluded to would have been far too insignificant to have 

 established the ichthyic nature of the Lepidosiren, \i, with coexisting gills and 

 lungs, the modifications of the other organic systems had agreed with those of 

 the Perennibranchians instead of with those of Fishes. For although it be true 

 that the fish-like modification of any single system is insuflUcient of itself to 

 determine the removal of the Lepidosiren from the Amphibia, in which it has 

 hitherto been placed, to the class of Fishes, yet it is impossible to avoid ar- 

 riving at that conclusion, when we consider the concurrence of ichthyic cha- 

 racters in so many parts of the organization of this most interesting species. 

 The combination of cycloid scales, mucous ducts, quasi-fins supported each 

 by a many-jointed ray, a gelatino-cartilaginous vertebral style united to the 

 whole surface of the basi-occipital and not to two basilar condyles, the prfe- 

 opercular bone, the simple structure of the lower jaw, the double spines of 

 the neur- and haem-apophyses, the green colour of the ossified parts of the 

 skeleton ; — these external and osteological characters being associated with an 

 intestinal spiral valve, with the absence of pancreas and spleen, the position of 

 the anus anterior to the allantoid bladder, a diccelous heart, six pairs of bran- 

 chial arches with the gills concealed, the simple organ of hearing consisting 

 only of the acoustic labyrinth excavated in cartilage and provided with large 

 otolithes, and, lastly, the blind nasal sacs, — form a cumulative body of evi- 

 dence in proof that the Lepidosiren is a Fish, which far outweighs the 

 argument to the contrary, founded on the reptile-like development of its air- 

 bladder, and its conversion into an organ of aerial respiration. 



The weight of this argument is, in fact, very much diminished by the close 

 approximation which certain of the abdominal Fishes, called 'Sauroid' by 

 M. Agassiz, make to the Lepidosiren in the lung-like structure of the air- 

 bladder. In the Freshwater Amia Cuvier states that its swim-bladder is as 

 cellular as the lung of a Reptile* : and this genus also agrees with the Lepi- 

 dosiren in the absence of pyloric csecal appendages. In the genus Lepidosteus, 

 again, Cuvier describes the air-bladder as being as cellular as in the Amia, 

 and occupying the whole length of the abdomen f. 



* " La vessie natatoire est celluleuse comme un poumon de Reptile." Rigne Anim. ii. p. 327. 

 t Loc. cit. p. 329. 



3 A 2 



