488 



Reviews — Barrande's Silurian Cephalopoda. 



includes the genera Goniatites and Badrites, the last Ascoceras, 

 Aphragmites and Glossoceras, Barr., whilst the Nautiliclce includes 

 twelve genera, embracing all the varieties of form of shell, from the 

 straight Orthoceras to the perfectly coiled Nautilus and Trochoceras. 



The number of species derived from the twelve types of JSfautilidcs 

 is 165, representing about one-third of the 478 forms which charac- 

 terize Fauna II. in all the Silurian countries. 



Thus at the outset of this group we find it largely represented 

 both in genera and species. About three-fourths of the 165 species 

 mentioned above are found by M. Barrande to be extremely local; this 

 would seem to contradict the idea of the free pelagic habits of these 

 moUusca ; there may have been, however, other impediments ; for 

 the world-wide homogeneous conditions of climate in Silurian times, 

 is, after all, only an assumption, whilst land barriers may have 

 opposed the migration of marine faunas, even more effectually than 

 they do at the present day. 



The following Table cannot fail to interest English palaeontologists, 

 giving as it does a summary of the British Cephalopoda. 





1 



Silurian Faunas. 



i 



a 



Pi 

 P. 



i 



p< 

 p< 



1 



1 



England, Scotland, 

 AND Ireland. 



I 



'•3 



a 





II. 



III. 



i 1 





d 



1 





> 



a 



T3 





i 







gS ^ 





yA 



ij o 



C8 



3 



^T3 



h4 



Ph 



"3 



1 



' 



.2 



n 



Number of types in each stage. 



1 ] 





4 



5 



4 



5 



7 





1 



Cyrtoceras, Golf. 



• 1 ] 





1 



7 



3 



2 



4 



. 



18 



3 



15 



2 



sub. gen. Piloceras, Salt, 









2 



. 



. 



. 



. 







2 



. 



2 



3 



Orthoceras, Breyn. 









6 



23 



15 



18 



19 







81 



25 



56 



4 



?,\ib.g&\\. Endoceras, Hall. 









1 



1 



. 



. 



. 







2 



. 



2 



5 



Zituites, Breyn. 









. 



b 



2 





1^ 







8 



1 



7 



6 



Gomphoceras, Sowby. 













1 



. 



1 



. 







2 



. 



2 



7 



Tretoceras, Salter. 













. 



1 



. 



1 







2 



. 



2 



8 



Phragmoceras, Brod. 













. 





3 



3 







6 



2 



4 



9 



Trochoceras, B.H. 













. 





1 



1 







2 



1 



1 



10 



Ascoceras, Barr. 













• 



• 





1 







1 



• 



1 





Appearance by stages. 



• l> 





10 



37 



21 



25 



30 



. 



124 



32 



92 













Fauna 



69 



55 







Reappearances between 











different stages to be deducted 



9 

 60 



12 

 43 











103 







Eeappearances between the II. 



and III. 









Faunas to he deducted 







]1 









Total number of distinct 



Bri 



tish s 



peeies... 



9 



2 











