342 Prof. Owen’s Description of the Lepidosiren annectens. 
Beyond these rudiments of a gustatory organ the membrane of the mouth is 
smooth, slightly puckered into irregular longitudinal folds, and gradually 
contracting as it passes along the interspace of the branchial openings to the 
orifice of the pharynx. This orifice* is much smaller and more suddenly con- 
tracted than in Fishes generally, or the Perennibranchiate Reptiles: it is also 
defended by a semicircular valvular fold f, which closes it from below. The 
esophagust is scarcely an inch in length; its lining membrane is puckered 
longitudinally : about three lines from the pharyngeal orifice, at the lower 
part of the œsophagus, is the laryngeal fissure$, or the orifice of the ductus 
pneumaticus: the fissure is one line in length, and is pierced in the posterior 
part of a cartilaginous plate], which extends forwards to the base of the valve 
of the pharyngeal aperture, where it terminates in a rounded edge, a line in 
breadth: this cartilage or rudimental thyroid is here obviously subservient to 
the maintenance of the patency of the esophageal canal anterior to the glottis; 
and the remarkable fact of the presence of a sensitive epiglottis is perhaps ex- 
plicable on the principle of its correlation with the above structure. 
The cesophagus gradually expands into a pyriform but not wide stomach, 
which both in its form and diameter so nearly resembles the intestine that the 
limits between the two are outwardly not very easy to define. Both cesophagus 
and stomach are situated in the same continuous Straight line as the rest of 
the alimentary canal. A slight constriction indicates the pyloric extremity of 
the stomach. The tunics of the stomach are pretty strong : 
brane has a smooth surface, and, in the specimen dissected, it 
composed, apparently by the action of the gastric juice, 
occurrence in Fishes. 
its lining mem- 
was partly de- 
which is a common 
The pylorus opens into the intestine by a circular 
valvular fold of the mucous membrane**, the margins of which are crenate. 
Before describing the rest of the alimentary canal, a few words may be pre- 
mised on the structure of the abdominal cavitytt. This commences about 
half an inch behind the pectoral filamentary fins, and extends about half an 
inch beyond the anus. It is Separated anteriorly from the pericardiac cavity 
as in Fishes and Perennibranchiate Reptiles, by a distinct transverse iita. 
* Tas. XXVI. fig. 1, c. T Ib. fig. 1, d. 
$ Tas. XXVI. fig. 1, e. | Ib. f. 
FE e, tt Ib, fig. 1. 
i TAB. XXV. fig. 2 d 
J Tas. XXV. fig. 2, b, 
