360 Prof. Owen's Description of the Lepidosiren annectens. 



Tab. XXVI. 



Circulating and Respiratory Organs of the Lepidosiren annectens, on the scale 



of one inch to half an inch. 



Fig. 1. Branchial and pulmonary apparatus seen from the dorsal aspect. 

 a. First lobe of the tongue, b. Second lobe of the tongue, c. c. Di- 

 varicated sides of the pharyngeal aperture, which has been slit 

 open. d. Pharyngeal valve, e. Laryngeal aperture, f. Laryn- 

 geal or thyroid cartilage. The figures 1, 2, 3, 4 & 5, indicate the 

 interspaces between the six branchial arches on each side, which 

 conduct the water to the branchial chamber, k. The membra- 

 nous trachea or ductus pneumaticus : its communication with the 

 right lung is shown. 

 2. The same parts, with the heart, seen from the ventral aspect, a. The 

 auricle ; the letter is placed on the left appendix, b. The ventricle, 

 laid open to show the termination of the vena pulmonalis, in which 

 a black bristle is placed ; the wide orifice of the auricle, and the 

 aortic opening through which a white bristle is passed, c. The 

 bulbus arteriosus, laid open to show the longitudinal valvular pro- 

 cesses in its interior, d. Pericardium, e. Vena cava abdominalis. 

 f. Vena pulmonalis. g. Arterial trunk common to the systemic, 

 branchial and pulmonary circulations. The figures 1, 2, 3, 4, 5 & 6, 

 indicate the branchial arteries on each side, of which the 2nd and 

 3rd chiefly go to form the pulmonary artery, /. m. m. The two 

 divisions of the pulmonary artery, for the two lungs, n. n. The 

 two corresponding veins, which return the aerated blood toy. 



Tab. XXVII. 



Fig. 1. A scale of the Lepidosiren annectens, magnified eight diameters. 



a. The inserted margin ; b. the thick cuticle reflected from the poste- 

 rior margin. 

 2. Mouth of the Lepidosiren annectens, twice natural size. 



a. The intermaxillary teeth, b. The three projecting angular pro- 



