1870.] (@SOPHAGUS OF SAUROPSIDA. 285 
fibre was not found to compose the sheath of the cesophagus of either 
Birds or Reptiles, while a coat of this fibre was always seen to invest 
more or less of the cesophagus of Mammalia and Fishes. Here, 
then, is a remarkable character in which Birds and Reptiles agree 
together and differ from Mammals and Fishes. 
Nor is it less noteworthy that while Sauropsida are thus distin- 
guished by the absence of striated muscular fibre on the cesophagus, 
they are, on the other hand, equally distinguished by the presence 
of this fibre within the eye. At least I have never found striated 
muscular fibres in the eye of any mammal or fish, nor have I ever 
failed to find those fibres in the eyes of Sauropsida; and this agrees 
with the older observations of other anatomists. But further re- 
searches are yet required on this subject. 
So, too, of the cesophageal sheath, both in the larval and perfect 
states, of Batrachia. As of Lepidosiren, a reputed fish, the blood- 
disks, according to my observations (Ann. Nat. Hist. October 1848, 
and Proc. Zool. Soc. 1862, fig. 17, p. 101), have a Batrachian 
character, it would be interesting and instructive to compare the 
cesophageal sheath of this creature with the same part of other 
allied vertebrates. In my note-book occurs the following account : 
—‘ Dec. 14, 1848. Lepidosiren from the West Coast of Africa: 
cesophagus membranous, wide and very dilatable, many striated 
muscular fibres mixed with smooth ones on the gullet backwards, as 
far as the hind end of the pericardium; the cesophagus a third of 
an inch further back, and thence to the stomach, quite destitute of 
any thing like striated muscular fibre.” This examination is at 
present worthless, from a want of the comparisons above mentioned, 
but may prove valuable whenever they are made. 
As already noticed, I have never found the whole cesophagus of 
Fishes and Mammalia destitute of a sheath of striated muscular 
fibre; and in certain sections of the class Mammalia the extent of 
that sheath is so different as to afford, so far as my observations 
have gone, good diagnostics. Thus in the Rodentia and Ruminantia 
this striated fibre does, and in Man and Quadrumana does not, invest 
the cardiac end of the cesophagus. And in different sections of one 
and the same order there may be similar differences; of the Car- 
nivora, e.g., the striated muscular fibre does not clothe the cardiac 
extremity of the cesophagus in the Felidae, but extends quite to that 
termination in the Urside. 
That such differences are always invariable cannot, in the present 
state of our knowledge, be peremptorily affirmed; but that they are 
constant in many vertebrates is certain. How far such characters 
may tend to favour the validity of the great group of Sauropsida, 
or of only the two primary vertebrate sections of Pyrenzemata and 
Apyreneemata (Proc. Zool. Soc. 1862, p. 91, and Journ. Anat. and 
Phys. v. 2), remains to be seen by the light of more knowledge. 
Finally, when all the diagnostics between Sauropsida and Mam- 
malia are well and truly reviewed, it now appears that the characters 
furnished by the intimate structure of the muscular fibre must receive 
_ more attention than has hitherto been given to them. 
Proc. Zoou. Soc.—1870, No. XX. 
