14"J BULLETIN OF THE NATURAL HISTORY SOCIETY. 



POSTSCRIPT. 



Since writing the above, it ha.s seemed to the author desirable to 

 make a broader distinction between the .Sardinian and American 

 species of Metadoxides than that given above. He has heretofore 

 depended upon the view of the Sardinian succession given by Bar 

 rande and Meneghini, from which one may infer the presence of two 

 Cambrian faunas in Sardinia, the lower containing Olenopsis, Meta- 

 doxides, Paradoxides, etc., and the upper Giordanella (Asaphus, 

 Menegh.) Neseuretus, etc. 



JBornemann, however, seems to throw doubt upon the entire separ- 

 ateness of these faunas, when he says that remains of GiordaneH" are 

 found with Metadoxides armatiis* If this is the case it will carry 

 the whole Sardinian Cambrian fauna to a higher plane, and imply the 

 separation of these by a wider space of time from the Newfoundland 

 species described above. 



Meneghini's view would admit of the following arrangement of the 

 Sardinian as compared with the Atlantic North American Cambrian 

 faunas. 



ATLANTIC NORTH AMERICA. SARDINIA. 



Giordanella Fauna. 



,, ( Dictyonema Famni 



/ >//"/ Peltura Fauna. 



Cambrian. 1 Olenus Fauna. 



Olenopsis Fauna. 



i Paradoxides Fauna. 



Lower ) Newfoundland species | 



Cambrian, j described in this article J 



' Protolenus Fauna. 



In this view the lower fauna of Sardinia might be regarded as 

 intermediate homotaxically, between the Paradoxides and Olenus 

 faunas. If, however, Bornernann's observation is to be relied upon, it 

 seems to me that the whole fauna must be carried to the Upper Cam- 

 brian, notwithstanding the presence of a Paradoxides. It is therefore 

 desirable to emphasize the point in which the Newfoundland species 

 differs from the later, and supposed derived forms of .Metadoxides, 

 found in Sardinia, and apply to them sub-generic names, beginning 

 w it h the most primitive. 



1 . Species baving a widely expanded front in the cephalic Bhield; somewhat 

 prolonged eyelobes; short posterior extension of the dorsal suture. No costs 

 on tin- -nil- lobes "t i In- pygidium. Catadoxides n. subgen. Example 

 ( '. maynifiens. 



•_'. Species baving a compacted front to the cephalic shield, short eyelobes, 

 prolonged posterior extension of tin- dorsal suture. 



'/. \<> cost a' mi the sides lobes of the pygidium. M bt idoxides, sens, strict. 

 Ex .1/. toromis. 



/;. One or more pairs of costse one the side lobes of the pygidium. Ana 

 doxides n. suk gen. Ex. .1. armatus, .1. Bornemanni (A. arenosus?) 



►VereteineruDgen descambriscben Bcbichtensystem derlnsel Sardinian, p. 166, Halle. 1891. 



