762 EXPLANATION OF PLATES. 



corresponding to another on the superior maxillary bone a', 

 which has been removed to the side and figured apart. 



Fig. 5. Head of Anableps tetrophthalmus, p. 95. 

 Fig. 6. Chironectes pictus, p. 141. 



Fig. 7. Head of Osphromenus olfax, after CUVIER et VALENCIENNES, 1. 1. 

 PL 205, to shew the convoluted appendages above the gills, 

 which are here exposed, pp. 201, 202. 



PLATE IV. REPTILES. 



Fig. 1. Heart with the origin of the arteries of a Crocodile or Caiman, 

 Crocodilus sclerops, p. 315. R, o, right auricle which on the 

 anterior or ventral surface covers a large part of the right ven- 

 tricle. L, o, left auricle, smaller and placed more on the 

 dorsal surface. In front of the ventricles is placed a large 

 arterial sac; from this 5 stems arise; 1, pulmonary artery; 

 2, descending aorta, which curves behind the trachea or the 

 left bronchus; 3, left branch of the ascending aorta; 4, right 

 branch of the ascending aorta; 5, most to the right side, a 

 second descending aorta which curves over the trachea or over 

 the right bronchus. Thus the two stems, 2 and 5, forming an 

 arterial ring round the oesophagus, descend and unite to form 

 the aorta abdominalis. The right stem 4 of the ascending 

 aorta forms the subclavian artery in this species only ; from the 

 left stem, on the contrary, of the ascending aorta the arteria 

 carotis a, c, arises, which, only when it has reached the base of 

 the cranium, divides into a right and left carotid. Compare 

 pp.^17, 218. 



Fig. 2. Posterior surface of the skull of Rana cutipora DUM. et BIBR. 

 p. 250, the left side omitted, natural size, to shew the two 

 occipital condyles ft, one of the characters of the Reptilia di- 

 plopnoa. * The auditory ossicle of the right side, which extends 

 from ihefenestra ovalis to the tympanic membrane. 



Fig. 3. Skull of a young Crocodilus Uporcatus, also seen from behind, 

 t Unpaired occipital condyle, one of the characters of the 

 Reptilia Jiaplopnoa, p. 255. 



Fig. 4. Skull of Trigonocephalus rliodostoma, p. 261, as an example 

 of the venomous serpents; k, the quadrate bone; I external, 



