ADDITIONS AND CORRECTIONS. 



The two species of Tuebo, page 12, probably do not strictly belong to this genus, but are 

 congeners of those in the Trenton limestone, which I have termed Holopea. They are not 

 Pleurotomaria nor MurchisonitB ; the perfect specimens never exhibiting any spiral band, 

 carina or marginal indentation. 



377. 8. AMBONYCHIA MYTILOIDES. 



Pi.. XXXm*. Fig. 2. 



Obliquely ovate, narrowing and acute at the beak ; posterior slope obtusely subcarinated ; 

 anterior margin straight above and rounded below ; surface (in the cast) presenting some 

 obscure concentric lines. 



The specimen is a cast, and the surface markings are unknown. It is quite distinct in 

 form from either of the other species of the genus, being more acute at the beaks than any 

 of them, and it is not as strongly marked by radii as the species of the Hudson-river group. 

 It is an interesting fact to show that this generic type commenced its existence almost with 

 the dawn of organic life ; continuing, in the several forms already given, to the termination 

 of the Hudson-river group. 



Position and locality. In the lower crystalline strata of the Chazy limestone at Chazy. 



63. 7. ORTHOCERAS MONILIFORME ( p. 35 ). 



This species should be placed Under the Genus Ormoceras, from the character of the 

 siphuncle. 



Gends PHYTOPSIS, and species ( pag. 38, pi. 8 & 9 ) . 



A further examination of these peculiar fossils has convinced me that they belong rather 

 to the ZooPHYTA than to Plants ; though it is impossible, with our present knowledge, to 

 decide their true relations or associates. The examination of a large number of specimens, 

 with the best glasses in my possession, has shown no pores upon the surface ; and the 

 internal structure, though similar to plants, is the kind of structure which plants exhibit 

 under a high magnifying power, and not to the naked eye as in these fossils. 



40* 



