The Lepidosiren: a Fish? or a Reptile? 467 
conclusion that this same Lepidosiren is a Reptile. This dif- 
ference of opinion admits of an easy explanation from the ab- 
normal character of this animal, but proves the want of new 
arguments, such as may turn the scale on one side or other. 
I thought, consequently, that it would be useful to examine 
anew the anatomical structure of the Lepidosiren; and as the 
Museum of the Jardin du Roi possesses a fine specimen, I 
begged M. Bibron, assistant naturalist in this establishment, 
to have the kindness to make a dissection of it; he has most 
obligingly done so, and has thus ascertained the accuracy of 
the descriptions given by M. Bischoff. 
One of the reasons upon which Mr. Owen most insists for 
placing the Lepidosiren amongst Fish, is the want of communi- 
cation between the nasal cavity and the mouth; but M. Bischoff 
asserts, that in the species which he dissected there exist hinder- 
nostrils (arriére-narines) opening into the cavity of the mouth 
‘near to the commissure of the lips. I also saw these posterior 
openings of the nasal cavity in the Lepidosiren paradoxa dis- 
sected by M. Bibron, and their abnormal position appears to 
be in part explained by the absence of superior maxillary 
bones. M. Bibron has also satisfied himself of the existence 
of the two auricles of the heart, described by M. Bischoff, so 
that in this important respect the Lepidosirven stands remote 
from Fish, and approaches nearer to most Reptiles. Lastly, 
he compared the structure of the pulmonary sacs of the Lepi- 
dosiren with that of the natatory bladder of Lepisosteus and 
Amia, and he observed that in the former this organ com- 
pletely resembles the lungs of several Reptiles; whilst in the 
two fish which we have just mentioned, the cells of the nata- 
tory bladder are much less compressed, less regular, and ap- 
parently less vascular. One of the lungs, that on the right 
side, stretches almost the whole length of the abdomen; but 
the other is much shorter, a disposition which is very com- 
mon among the Reptiles. We should remark, that it is also 
the right lung which is greatly developed in the Ophidians, 
whilst the left lung remains more or less rudimentary. 
This difference of structure between the pulmonary pouches 
of the Lepidosiren and the air-bladder of Lepisosteus and 
Amia, would certainly not suffice to negative the analogy 
which Mr. Owen allows between these organs, and to draw 
from the presence of the former in the Lepidosiren a pe- 
remptory argument in favour of the herpetological charac- 
ter of this animal; but there is another consideration which 
appears not yet to have struck zoologists, and which I 
think should have some weight in this discussion. ‘The 
lungs of Mammalia, of Birds and of Reptiles, as every one 
2H 2 
