65 



Calciferous Fauna. 



Asaphus, 1; Amphion,2; Bathyurus, 6; Bathyurellus, 2 ; Do- 

 licJiometopus, 3. Total, 14. 



Potsdam Fauna. 



Agnostus, 4; AgSaspis, 6 ; Amphion, S ; ArlonelBus, 4; 

 BathyL3rus,4; Bat^ynotus,!; ChariocepSialus, h CEamac- 

 tjchnites, I ; Conocephalites, 23; CrepicephaSus, 2; 

 Dikelocephalus, !0; liidsnurus, I ; MenocephaBus, I ; Lon- 



choeephalus,2; ©Ser6eS8us,2; Pemphigaspis, h Protich- 

 nites, 6; Ptyc^aspis, I ; TrEarthrelSa, I- Total, 67. 



In the above lists the genera printed in black-letter are those that occur 

 in the Potsdam ; those in italics belong to the primordial type, but have 

 not yet been found in the Potsdam. All the others are members of the 

 second fauna of Barrande, except, indeed, Endymionia and Shumardia, 

 which are new genera, whose geological range is as yet undetermined. 

 Cre2ncep7ialus,PtycJiaspis and Bathynotus are placed in the L^vis faunae, 

 but with their number not indicated, because the species are included in 

 Likelocevhalus and Bathyurus. The lists show, so far as the proposition 

 can be demonstrated by genera alone, that the true place of the L6vis 

 formation is between the Potsdam and the Trenton groups, not below the 

 Potsdam, as is still maintained by some observers. 



If we examine how far these several faunae are connected together 

 by species, we find : — 



1. Not a single species of the large fauna of the Potsdam is known to 

 pass upwards. 



2. Of the Calciferous fauna, four species QAsapJius canalis, Amphion 

 Salteri, Bathyurus Gordai and B. conicus) pass upwards into the 

 L^vis formation. And one of these (^A. canalis) ascends into the Chazy. 



3. Of the Levis fauna, two species (^A. canalis and Cheirurus proli- 

 ficus') pass upwards into the Chazy. 



4. One trilobite only QAsajjhus platycephalus), and that doubtfully 

 identified, is common to the Chazy and Trenton. It is also worthy of 

 notice that the peculiar group of the genus Cheirurus, with a spine on 

 the head, has only been found, in America, in the L^vis formation, and 

 in the Chazy, (see C. perforator, p. 275 ; C. Glaucus and C. Satyrus, 

 p. 323.) And further that the genus Remopleurides has, as yet, been 

 found in America only, in the same two formations. 



Proceeding, next, to the other orders and classes, such as the Brachio- 

 poda. Gasteropoda, Cephalopoda, &c., it is quite clear that the Ldvis 

 fauna is, upon the whole, distinct from all the others, although a few 

 species are common to it and the Calciferous, or to it and the Chasiy. 



