Prof. Owen'& Description of the Lepidosiren annectens. 359 



Tab. XXV. 



Fig;. 1 . Abdominal cavity and pericardium of Lepidosiren annectens. 



a. JMylo-hyoideus. b. Sterno-hyoideus. c. Coraco-hyoidens. d. Fibrous 

 membrane covering the pericardium e. f. Serous layer of the 

 peritoneum reflected from the pericardiac septum, g. Right ova- 

 rium, h. Liver, i. Gall-bladder. Â-. Intestine. /. Mediastinal 

 fold of the serous layer of the peritoneum, m. A bristle passed 

 thrt)ugh the peritoneal outlet. ». The same through the anal orifice. 

 o. The same through the uro-genital outlet. (The common cloacal 

 passage is removed with the skin.) 



2. Digestive organs of Lepidosiren annectens. 



a. Œsophagus. b. Stomach, laid open. c. Pyloric valve, d. Spiral 

 valve of intestine, e. Rectum, f. Liver, g. Gall-bladder, h. Val- 

 vular termination of ductus choledochus. i. Vena cava hepatica. 



3. Heart, gills, and lungs in situ, of Lepidosiren annectens. 



a. Auricle ; the letter is placed on the right appendix, b. Ventricle. 

 c. Bulbus arteriosus, d. The pericardium, e. The abdominal vena 

 cava. f. The muscular stratum dissected off, to show^. the mucous 

 membrane of the branchial chamber of the right side. Both are 

 removed on the left side, to expose the gills and branchial arches : 

 bristles are represented as passing from the mouth through the 

 five interspaces of the branchial arches, h. The hyoid arch. 

 /. /. The lungs : that on the right side is laid open to show its cel- 

 lular structure. <r. The left coracoid turned outwards, to show 

 the heart : the right coracoid is in situ, with the pericardium at- 

 tached to it. 



4. Front view of the jaws and teeth of Lepidosiren annectens. 



5. View of the upper or working surface of the dental plates of the lower 



jaw. 

 All the figures in this plate are of the natural size. 



VOL. XVIII. 3 B 



