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 Perenni branchiate Reptiles : it is also 

 defended by a semicircular valvular fold f , which closes it from below. The 

 oesophagus:|: 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 oesophagus, 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 oesophageal caiial 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 oesophagus 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 oesophagus 

 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: its lining mem- 

 brane has a smooth surface, and, in the specimen dissected, it was partly de- 

 composed, apparently by the action of the gastric juice, which is a common 

 occurrence in Fishes. 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 cavityff. 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 septum. 



