642 



Defrance, in a work * full of new and ingenious 

 ideas, not only recognizes this preponderance 

 of the univalves in the number of kinds ; but 

 also observes, that in 5500 fossil species of 

 univalve, bivalve, and multivalve shells, con- 

 tained in his rich collections, there are 3066 

 univalve, 2108 bivalve, and 326 multivalve ; the 

 univalve fossils are therefore to the bivalve = 

 3:2. 



XIII. FORMATION OF PYROXENIC AMYGDALOIDE 

 AND PHONOLITE, BETWEEN ORTIZ AND CERRO DE 

 FLORE S. 



I place at the end of the formations of Vene- 

 zuela the pyroxenic amygdaloide soil, and the 

 phonolithic (porphyrschiefer), not as being the 

 only rocks which I consider as pyrogenous> 

 but as those of which the entirely volcanic 

 origin is probably posterior to tertiary soil. 

 This result is not owing to the observations I 

 made at the southern declivity of the Cordillera 

 of the shore, between the Morros of San Juan, 

 Parapara, and the Llanos of Calabozo. In 

 that region, local circumstances would rather 

 lead us to regard the amygdaloides of Ortiz as 

 linked to a system of transition rocks (amphi- 

 bolic serpentine, diorite, and carburated slate 



t Table of organised fossil bodies, 1824, p. 51, 125. 



