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, if, 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 insufficient 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 pree- 
opercular bone, the simple structure of the lower jaw, the double spines of 
the neur- and hæm-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 dicœlous 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 aérial 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 4mia 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 czecal 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. 
La vessie natatoire est celluleuse comme un poumon de Reptile." Règne Anim. ii. p. 327. 
T Loc. cit. p. 329. 
342 
